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TO  THE 

LIBRARY  OF  THE 
MEDICAL  DEPARTMENT 

OF  THE 
UNIVERSITY  OF  CALIFORNIA 


UNIVERSITY  OF  CALIFORNIA 

MEDICAL  CENTER  LIBRARY 

SAN  FRANCISCO 


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GIFT   OF 


TO  THE 

LIBRARY  OF  THE 
MEDICAL  DEPARTMENT 

OF  THE 
UNIVERSITY  OF  CALIFORNIA 


UNIVERSITY  OF  CALIFORNIA 

MEDICAL  CENTER  LIBRARY 

SAN  FRANCISCO 


Practical  Work  in  Physiology 


T 


Directions  for  Class 
in   Practical   Physiology 


o 


ELEMENTARY  PHYSIOLOGY  OF  MUSCLE  AND 

NERVE  AND  OF  THE  VASCULAR 

AND  NERVOUS  SYSTEMS 


— "     BY 


E.  A..SCHAFER,   LL.D.,  F.R.S. 

Professor   of  Physiology  in   the    University   of  Edinburgh ;  formerly 
Jodrell  Professor  of  Physiology  in  University  College t  London 


WITH  DIAGRAMS 


LONGMANS,    GREEN,    AND    CO 

91  AND  93  FIFTH  AVENUE.  NEW  YORK 


COPYRIGHT,  1901,  BY 
LONGMANS,  GREEN,  AND  CO. 

All  rights  reserved 


.  J. .Little  &  Co. 


c       » * .  •*       c   I1  I          *  « 
i  «•    *  . »    • . « «* c  *«••*•*' 


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190' 


PREFACE 


THE  following  directions  are  based  upon  an  ex- 
perience of  many  years  in  University  College,  Lon- 
don, where  such  a  course  of  instruction  was  first 
instituted  by  Professor  Burdon-Sanderson.  Al- 
though they  have  long  been  in  use  I  have  now 
had  them  printed  for  the  convenience  of  my 
Edinburgh  students.  There  are  several  text-books 
dealing  with  the  same  subject,  but  they  are  all 
more  elaborate,  and  concern  themselves  with  many 
problems  which  the  average  medical  student  can- 
not be  expected  to  investigate  for  himself.  On 
this  account  perfectly  simple  instructions  dealing 
only  with  such  elementary  exercises  as  can  readily 
be  worked  out  by  even  a  large  class,  may,  it  is 
hoped,  prove  useful  to  other  teachers  and  students 
than  those  for  whom  they  are  primarily  intended. 


205 


' 


205 


Practical    Physiology 


CHAPTER    I. 

Batteries. — A  voltaic  element  or  cell  usually 
consists  of  two  metals— e.g.,  zinc  and  copper — im- 
mersed in  a  fluid  such  as  dilute  sulphuric  acid,  and 
the  changes  (movements  of  ions)  which  occur  under 
these  circumstances  in  the  fluid  produce  a  disturb- 
ance of  electrical  equilibrium  in  the  cell  which 
manifests  itself  as  a  difference  of  electrical  potential 
or  pressure  at  the  metals.  If  wires  are  connected 
to  these  it  is  found  that  the  end  of  the  wire  con- 
nected with  the  copper  or  negative  metal  is 
charged  with  positive  electricity,  and  that  connected 
with  the  zinc  or  positive  metal  is  charged  with 
negative  electricity  ;  these  ends  are  called  the  pos- 
itive pole,  or  anode,  and  the  negative  pole,  or 
kathode,  respectively.  The  anode  is  said  to  be  in 
a  condition  of  higher  potential  and  the  kathode  in 
one  of  lower  potential,  and  when  they  are  joined 
electrical  equilibrium  tends  to  re-establish  itself 
in  the  circuit  thus  closed.  It  is  common  to  speak 
of  a  current  as  flowing  from  the  anode  to  the 
kathode  outside  the  battery  and  from  the  zinc  to 


PRACTICAL    PHYSIOLOGY 


the  copper  inside.1  The  amount  of  this  current 
depends  upon  the  difference  of  potential  produced 
within  the  cell.  This  is  diminished  by  any  in- 
crease of  resistance  to  the  flow  of  electricity 
whether  occurring  within  the  cell  or  in  the  outside 
circuit.  Electromotive  force  (E.M.F.)  is  measured  in 
volts  ;  thus  the  E.M.F.  of  a  Daniell  cell  is  1.079  volts. 


Anode.. 


Copper,— 


Kathode. 


Zinc. 


mmm .Dilute  sulphuric  acid. 


FIG.  i.— VOLTAIC  COUPLE. 

It  may  be  increased  by  coupling  two  or  more  cells 
together  in  series,  the  zinc  of  one  connected  with 
the  copper  of  the  next,  and  so  on. 

If  electricity  be  generated  simply  by  immersing 
plates  of  zinc  and  copper  into  acid  the  chemical 
action  which  ensues  causes  bubbles  of  hydrogen 

1  Within  the  battery  the  electrical  potential  is  highest  at  the 
zinc,  which  is  therefore  here  the  anode,  and  lowest  at  the  copper, 
which  is  here  the  kathode. 


PRACTICAL  PHYSIOLOGY 


FIG.  2. — DIAGRAM  OF  A  VOLTAIC  COUPLE.    Z,  ZINC  ;  C,  COPPER. 

gas  to  form  on  the  copper,  and  this  not  only  intro- 
duces a  resistance  to  the  flow  of  current  through 
the  cell,  but  the  hydrogen  being  electropositive 
tends  to  set  up  a  current  (polarisation  current)  in 
the  opposite  direction  in  the  cell  and  circuit ;  from 
both  these  causes  the  original  E.M.F.  of  the  cell 
becomes  rapidly  weakened. 

To  obviate  this  effect  Daniell  placed  the  copper 


Copper  pot. 


Zinc. 

Porous  pot  containing 
dilute  sulphuric  acid. 


-Sulphate    of     copper 
(saturated  solution). 


FIG.  3.— DANIELL  CELL. 


PRACTICAL   PHYSIOLOGY 


plate  in  a  saturated  solution  of  copper  sulphate 
and  introduced  a  porous  pot  to  separate  this  from 
the  dilute  sulphuric  acid  in  which  the  zinc  is  im- 
mersed. The  zinc  then  dissolves  in  the  acid,  dis- 
placing hydrogen  ;  the  hydrogen  in  its  turn  dis- 
places copper  from  the  copper  sulphate,  and  the 


Zinc 


Carbon. 

Manganese  dioxide 
in  porous  pot. 


Ammonium  chloride 
solution. 


FIG.  4. — LECLANCHE  CELL. 

displaced  copper  is  deposited  on  the  copper  plate, 
so  that  no  bubbles  of  hydrogen  are  formed  upon 
the  metal,  and  if  the  copper  sulphate  solution 
is  kept  saturated,  the  E.M.F.  of  the  cell  remains 
constant.  Commercial  zinc,  which  is  never  pure, 
must  always  be  "  amalgamated "  by  rubbing  its 
surface  with  mercury  after  it  has  been  cleaned  by 
dipping  into  acid. 


PRACTICAL   PHYSIOLOGY  5 

Other  constant  batteries  which  are  frequently 
used  in  physiology  are  that  of.  Grove,  where  the 
negative  plate  is  platinum  and  is  plunged  into 
strong  nitric  acid,  separated  from  the  sulphuric 
acid  containing  the  zinc  plate  by  a  porous  parti- 
tion ;  that  of  Bunsen,  which  is  similar  to  Grove's, 
but  with  a  negative  plate  of  carbon  ;  that  of  Le- 
clanche  (Fig.  4),  in  which  the  acid  is  replaced 
by  chloride  of  ammonium  and  the  place  of  the 
negative  plate  is  also  taken  by  carbon,  which  is 
surrounded  by  manganese  dioxide ;  and  that  of 
Grenet,  where  carbon  again  forms  the  negative 
plate,  but  where  a  single  fluid  is  used  (bichromate  of 
potassium  dissolved  in  dilute  sulphuric  acid),  in 
which  both  plates  are  immersed.  The  so-called 
"  dry  "  cells  are  modified  Leclanches.  The  positive 
plate  in  every  one  of  these  cells  is  amalgamated  zinc. 

Electrodes. — The  wires  used  in  physiological 
experiments  must  always  be  insulated,  either  with 
gutta-percha  or  with  silk  or  cotton  ;  in  the  latter 
case  the  insulation  is  rendered  more  effectual  by 
dipping  the  covered  wire  into  molten  paraffin. 
For  experimental  purposes  it  is  usual  to  place  the 
ends  of  the  wires  (which  must  be  clean  and  free 
from  the  insulating  material)  in  some  sort  of  holder, 
so  that  they  can  be  more  readily  applied  to  the 
tissue  which  is  to  be  investigated  ;  these  ends  are 
then  termed  the  electrodes.1-  They  are  often  made 

1  The  term  electrode  means  literally  the ' '  path  "  of  the  electric  cur- 
rent, and  in  this  sense  the  wires  throughout  are  electrodes.  But  it 
has  come  to  mean  technically  the  ends  of  the  wires  which  are  used 
to  apply  the  electric  current  to  a  given  object  (such  as  an  animal 
tissue). 


PRACTICAL   PHYSIOLOGY 


of  platinum  set  in  a  vulcanite  holder;  but  a  pair 
of  pins  with  fine  wires  soldered  to  their  heads, 
which  can  on  occasion  be  passed  through  a  small 
cork,  with  their  points  projecting  for  a  few  milli- 
metres, constitute  a  readily  improvised  and  efficient 


FIG.  5.— PAIR  OF  ELECTRODES  IN  CORK  OR  VULCANITE  HOLDER. 

pair  of  electrodes  for  most  class  purposes.  Like 
the  plates  of  the  battery  itself,  such  metallic  elec- 
trodes are  capable  of  becoming  polarised  when 
they  are  in  contact  with  the  moist  tissues,  and  a 
current  is  passed  continuously  between 
them  in  one  direction.  For  some  ex- 
periments it  is  necessary  to  obviate  this 
polarisation  of  electrodes  and  to  employ 
electrodes  which  are  not  polarisable. 
These  are  usually  made  by  taking  two 
small  pieces  of  glass  tubing  open  at  both 
ends,  either  straight  (Fig.  7)  or  curved 
(Fig.  8),  and  having  plugged  one  end  of 
such  tube  with  modelling  clay  moistened 
with  salt  solution,  filling  the  tube  with 
saturated  solution  of  zinc  sulphate,  and 

.  .  A 

plunging  an  amalgamated  zinc  rod  (to 
which  one  of  the  wires  of  the  circuit  is  soldered 
or  otherwise  attached)  in  the  zinc  sulphate. 

To  determine  which  of  the  two  electrodes  in  any 
case  is  the  anode  and  which  the  kathode  they  may 
be  placed  in  contact  with  a  piece  of  blotting  paper 


PRACTICAL   PHYSIOLOGY 


Saturated  solution  of 
zinc  sulphate. 


moistened  with  starch  so- 
lution containing  iodide 
of  potassium.  Iodine  is 
set  free  at  the  anode  and 
turns  the  starch  blue. 
Feeble  differences  of  elec- 
trical potential  are  de- 
termined and  estimated 
by  other  methods  (gal- 
vanometer, electrometer), 
which  will  be  studied 
later. 

Keys. — Any  apparatus 
which  is  used  for  inter- 
rupting or  diverting  the 
course  of  a  current  is 

called  a  key  or  switch.     The  keys  used  in  physio- 
logical experiments  are  arranged  to  close  and  open 


Clay  plug,  moistened 
with  salt  solution. 


FlG.    7. — NON-POLARISABLE    ELEC- 
TRODE. 


Zinc  wire. 


-Clay  plug  in  small  glass 
tube. 


-Zinc  sulphate  solution. 


FIG.  8.— SANDERSON'S  PATTERN  OF  NON-POLARISABLE  ELECTRODE. 


8 


PRACTICAL   PHYSIOLOGY 


the  circuit  (make  and  break  the  current)  by  con- 
necting the  wires  together  either  through  a  pool  of 
mercury  (inercury  key — Fig.  9)  ;  or  by  contact  be- 


FIG.  9.  —  MERCURY  KEY  IN  A  BATTERY  CIRCUIT. 

tween  a  platinum  plate  and  platinum  point  (contact 
key  —  Fig.  10),  as  in  the  Morse  key  ;  or  by  friction 
contact  between  two  brass  surfaces  {friction 


FIG.  10.  —  CONTACT  KEY  IN  A  BATTERY  CIRCUJT. 

as  in  that  known  as  du  Bois-Reymond's  (Fig.  n), 
and  in  the  ordinary  electric-light  switches.  They 
are  used  in  two  ways,  viz.  :  either  to  simply  close 


FIG.  ii. — FRICTION  KEY  IN  A  BATTERY  CIRCUIT;  DIRECT  METHOD  OF  USE. 

or  open  the  circuit  (direct  method}  ;  or  by  bridg- 
ing across  a  part  of  the  circuit  a  passage  with  very 
little  resistance  is  offered  through  the  key,  and  the 
current  is  thus  diverted  from  the  main  circuit  and 


PRACTICAL   PHYSIOLOGY  O 

from  the  electrodes  (short-circuit  met  hod — Fig.  12). 
For  this  purpose  du  Bois-Reymond's  key  is  espe- 
cially well  suited.  A  key  which  is  constructed  so 
as  to  cause  a  current  to  flow  either  in  one  direc- 
tion or  in  the  reverse  direction  in  a  circuit  is  called 
a  reverser  or  commutator.  One  of  the  most  con- 


FIG.  12.— FRICTION  KEY  ;   SHORT-CIRCUIT  METHOD  OF  USE. 

venient  is  Pohl's  commutator  (Fig.  13),  which  con- 
sists of  a  square  plate  of  vulcanite  or  other  non- 
conducting material  in  which  are  six  cups  of 
mercury  connected  with  terminals.  Four  of  the 
cups  are  joined  diagonally,  two  and  two,  by  crossed 
wires.  A  rocking  double  bridge  of  copper  serves, 
on  being  moved  to  one  side  or  the  other,  to  effect 
the  reversal. 


FIG.  13. — POHL'S  COMMUTATOR. 

If  the  crossed  wires  are  removed  the  Pohl  can 
be  used  as  a  switch  for  diverting  a  current  into 
one  or  other  of  two  circuits  (Fig.  14). 

Rheochords. — A  rheochord  is  an  apparatus  for 
dividing  a  constant  current  by  offering  a  circuit  of 
relatively  small  resistance  which  is  capable  of  being 
varied  so  that  a  variable  part  only  of  the  current 


10 


PRACTICAL   PHYSIOLOGY 


shall  pass  through  the  experimental  circuit.  It 
usually  consists  of  a  german-silver  or  platinum- 
iridium  wire  of  a  certain  known  resistance  (e.g., 


FIG.  14. — POHL'S  COMMUTATOR  USED  AS  SWITCH  (CROSS  WIRES  REMOVED). 

20  ohms),  to  the  ends  (Fig.  15,  a  and  b)  of  which 
the  battery  poles  are  connected  ;  a  certain  differ- 
ence of  potential  is  thereby  produced  at  the  two 


FIG.  15.— DIAGRAM  OF  RHEOCHORD. 


ends  of  the  wire.  With  one  of  these  ends  (a)  an- 
other wire  is  connected  ;  this  forms  part  of  the  ex- 
perimental circuit  through  which  a  portion  of  the 
battery  current  is  to  be  conducted  ;  this  circuit  is 


PRACTICAL   PHYSIOLOGY  II 

completed  through  a  wire  attached  to  a  rider  (r) 
which  slides  along  the  rheochord  wire. 

When  r  is  in  contact  with  b  the  whole  difference 
of  potential  between  a  and  b — this  difference  de- 
pending upon  the  E.M.F.  of  the  battery  and  the 
resistance  of  the  rheochord  wire — is  operative  in 
producing  a  current  through  the  experimental  cir- 
cuit. When  r  is  at  the  middle  of  the  rheochord 
wire  only  one-half  of  this  difference  of  potential 
comes  into  play,  and  so  in  proportion  to  the  dis- 


FIG.  16. — DOUBLE-WIRE  RHEOCHORD. 


tance  between  a  and  r  as  compared  with  the  whole 
length  of  the  wire.  Thus  if  the  wire  be  100  centi- 
metres long  and  r  be  placed  at  one  centimetre 
from  a  only  T^  of  the  total  difference  of  potential 
will  be  operative  and  a  proportional  current  will 
be  diverted  into  the  experimental  circuit.  When 
this  form  of  rheochord  is  to  be  used,  the  resistance 
of  the  experimental  circuit  must  always  be  very 
great :  this  is  invariably  the  case  in  physiological 
experiments. 

In  another  form  of  rheochord  (Poggendorff's) 
the  wire  is  doubled  on  itself,  and  a  rider  (r)  bridges 
across  and  forms  a  short  circuit  between  the  two 


12  PRACTICAL   PHYSIOLOGY 

parts  of  the  wire  (Fig.  16).  The  battery  circuit 
and  the  experimental  circuit  are  both  connected 
with  the  ends  of  the  wire.  When  the  rider  is 
brought  in  contact  with  these  ends  the  battery 
'current  is  completely  short-circuited,  but  when  the 
rider  is  moved  away  from  the  ends  a  gradually  in- 
creasing resistance  is  inserted  into  the  short  circuit 
formed  by  the  rheochord  and  its  rider,  and  propor- 
tionally more  of  the  battery  current  passes  into  the 
experimental  circuit. 

Induction  coil. — If  the  wires  of  two  separate 
circuits  are  at  any  point  near  to  and  parallel  with 
one  another  and,  in  the  one  circuit,  the  current  of 
a  battery  is  either  made  or  broken  by  the  closing 
or  opening  of  a  key,  an  induced  current  is  set  up 
in  the  other  or  secondary  circuit  at  the  instant  of 
such  closing  or  opening,  but  not  during  the  passage 
of  the  primary  current.  The  induced  or  secondary 
current  is  always  of  very  short  duration,  but  has  a 
much  higher  electromotive  force  than  the  primary 
or  inducing  current. 

In  order  to  multiply  the  inductive  effect  the  two 
circuits  always  take  the  form  of  closely  coiled 
wires  (Fig.  1 7)  (that  of  the  secondary  circuit 
being  very  fine  and  having  very  numerous  coils), 
and  to  still  further  increase  the  effect  the  primary 
coil  is  wrapped  round  a  core  formed  of  a  bundle 
of  soft  iron  wires  which  are  magnetized  and  de- 
magnetized on  the  closing  and  opening  of  the 
primary  circuit,  thus  enhancing  the  induction 
effects. 

For  physiological   purposes   the  induction    coil 


PRACTICAL   PHYSIOLOGY  13 

was  arranged  by  du  Bois-Reymond  so  that  the 
secondary  circuit  can  be  made  to  slide  nearer  to  or 
farther  from  the  primary  circuit  ;  since  with  the 
same  strength  of  battery  the  nearer  or  further  the 
coils  are  from  one  another  the  greater  or  less  is 
the  strength  of  the  induced  current.  The  varia- 
tion is  not,  however,  proportional  to  the  distance, 
but  approximately  to  the  square  of  the  distance. 
For  producing  single  make  and  break  induced 
shocks  the  primary  circuit  is  closed  and  opened 
with  a  simple  key.  For  multiple  induced  shocks 
most  coils  are  fitted  with  an  apparatus  for  auto- 

Secondary 

coil. „ 


_ —-Mercury  key 

bnort-cir-          \    t*y  /  /°  in  primary 

cuit  key -*— *JLJ- 


FIG.  17. — INDUCTION  COIL  ARRANGED  FOR  SINGLE  SHOCKS. 


matically  breaking  and  making  the  primary  circuit 
(Neef's  hammer).  This  will  be  understood  from 
the  diagram  (Fig.  18).  The  battery  current  is 
conveyed  from  the  terminal,  T3,  to  a  steel  spring, 
Sp,  having  a  bar  of  soft  iron  at  its  free  end,  and 
the  current  passes  from  the  spring,  which  has  a 
plate  of  platinum  upon  it,  to  the  platinum  point  of 
a  screw,  S*,  and  thence  through  the  primary  coil. 
Before  passing  back  to  the  battery  it  is  conducted 
through  a  small  electro-magnet,  M;  the  electro- 


14  PRACTICAL   PHYSIOLOGY 

magnet  being  thus  set  in  action,  draws  down  the 
iron  bar  and  with  it  the  spring,  which  leaves  the 
screw  and  breaks  contact  so  that  a  break  induced 
current  is  set  up  in  the  secondary  coil.  But,  the 
current  being  broken,  the  electro-magnet  is  no 
longer  active,  the  bar  springs  up  again,  and  con- 
tact is  re-established  between  the  spring  and  screw; 
this  produces  a  make  induced  current  in  the  sec- 
ondary coil.  Thus  the  spring  vibrates  to  and  fro, 
and  break  and  make  induced  currents  are  set  up  in 


Short-cir- 
cuit key 


Electrodes +\  v  Mercury 

key. 

FIG.  18. — INDUCTION  COIL  ARRANGED  FOR  AUTOMATIC  INTERRUPTION  OF  PRIMARY 

CIRCUIT. 

the  secondary  coil  many  times  a  second,  according 
to  the  rate  of  vibration  of  the  spring.  These  make 
and  break  shocks  are  unequal  owing  to  the  extra 
current  (see  below)  which  is  self-induced  within 
the  primary  coil,  and  which  diminishes  the  make 
effect.  This  inequality  is,  however,  got  over  by 
a  modification  introduced  by  Helmholtz.  In  this 
arrangement  (Fig.  19)  a  wire,  W ,  connects  the 
terminals,  7\  T3 ;  the  screw  S*  is  raised  alto- 


PRACTICAL   PHYSIOLOGY  15 

gether  away  from  the  spring,  and  the  screw  S2  is 
brought  nearly  up  to  the  spring.  The  battery  cur- 
rent passes  by  the  wire,  W,  from  the  terminal,  T\ 
directly  to  T\  thence  through  the  primary  coil 
and  through  the  electro-magnet,  Mt  which  draws 
down  the  iron  bar  and  brings  the  spring  in  contact 
with  the  screw,  S2.  A  large  part  of  the  battery  cur- 
rent now  goes  directly  back  to  the  battery  through 
this  contact,  and  is  diverted  from  the  primary  coil 
and  electro-magnet.  This  greatly  weakens  the 


FIG.  19. — HELMHOLTZ'S  ARRANGEMENT  OF  INDUCTION  COIL. 

current  through  the  primary  coil,  and  the  equiva- 
lent of  a  break  induced  shock  is  obtained  in  the 
secondary  circuit ;  for  any  sudden  variation  in  the 
current  of  the  primary  coil  is  effective  in  produc- 
ing an  induced  current  in  the  secondary  coil.  But 
the  electro-magnet  is  also  weakened,  so  that  the 
bar  and  spring  fly  up.  This  breaks  the  short-cir- 
cuiting contact  which  was  established  between  the 
spring  and  S2,  and  the  whole  current  again  passes 
through  the  primary  coil,  producing  the  equivalent 
of  a  make  induced  shock  in  the  secondary  circuit, 


1 6  PRACTICAL   PHYSIOLOGY 

and  so  on  automatically.  It  will  be  observed  that 
the  primary  circuit  is  never  actually  broken,  but 
only  short-circuited. 

The  above-described  apparatus  having  been 
studied,  the  following  experiments  are  to  be  per- 
formed : 

1.  Connect  up  a  cell  with  a  pair  of  wires,  intro- 
ducing a  simple  key  into  the  circuit  (Fig.  9).      Place 
the  free  ends  of  the  wires  on  the  tongue,  and  close 
and  open  the  key. 

2.  Repeat  this  experiment,  but  use  a  short-cir- 
cuiting key  (Fig.  12).      Note  that  the  effect  of  the 
current  upon  the  tongue  is  now  only  felt  when  the 
key  is  open. 

3.  Connect  a  cell  with  electrodes  through  a  com- 
mutator,  as   shown  in   Fig.    13.      Determine    with 
pole-reaction  paper  which  is  the  anode  and  which 
the  kathode  in  the  two  positions  of  the  bridge  of 
the  commutator.     Verify  this  by  following  out  the 
course  of  the  wires. 

4.  Connect  a  cell  with  the  upper  terminals,   T*, 
T2,  of  the  primary  coil  of  the  inductorium,  intro- 
ducing a  simple  key  into  the  circuit.      Connect  a 
pair  of  electrodes  through  a  short-circuiting  key  with 
the  terminals  of  the  secondary  coil,  and  slide  this 
coil  to  some  distance  from  the  primary  (Fig.  17). 
Place  the  electrodes  on  the  tongue.     Alternately 
close  and   open  the    key  in    the    primary    circuit. 
Notice    that    induction    shocks    are    obtained    on 
making  and  breaking  the  primary  circuit,  but  not 
during  the  passage  of  the  current.      Notice  that  the 
break  shocks  are  much  sharper   than    the  make. 


PRACTICAL   PHYSIOLOGY  17 

This  is  partly  due  to  the  fact  that  as  the  current  of 
the  primary  circuit  is  made  and  broken  induced  cur- 
rents (extra  currents)  are  formed  in  its  own  coils ; 
the  make  extra  current  of  closure  being  in  the  op- 
posite direction  to  the  battery  current  diminishes 
the  make  induced  current  in  the  secondary  circuit, 
while  the  break  extra  current  is  cut  off  by  the  open- 
ing of  the  primary  circuit.  The  sharpness  of  the 
break  effect  is  also  partly  due  to  the  fact  that  with 
the  keys  generally  used  the  opening  of  the  primary 
circuit  is  more  sudden  than  the  closure. 


Primary  coil 


FIG.  20.— EXPERIMENT  TO  SHOW  BREAK  "EXTRA"  CURRENT. 

5.  To  show  the  existence  of  the  "  extra  "cur- 
rents remove  the  secondary  coil  altogether  and 
connect  up  the  primary  coil  by  T1  and  T*  with  a 
battery  and  keys  in  the  way  shown  in  Fig.  20. 
Place  the  electrodes  on  the  tongue.  Make  and 
break  the  battery  circuit  by  closing  and  opening 
the  key,  K\  If  this  is  done  when  the  pri- 
mary coil  is  included  in  the  circuit  (i.e.,  with  K* 
open)  the  effect  is  greatly  enhanced  by  the  "  extra  " 
current,  but  if  the  coil  is  shunted  out  by  clos- 


1 8  PRACTICAL   PHYSIOLOGY 

ing  K*  the  stimulus  is  hardly  perceptible  to  the 
tongue. 

6.  Instead  of  placing  the  simple  key  in  the  pri- 
mary circuit  place  it  in  a  side  circuit  (Fig.  21).    On 
closing  and  opening  the  key,  shocks  are  still  pro- 
duced in  the  secondary  circuit,  although  the  current 
through  the  primary  coil  is  not  made  and  broken, 
but  only  strengthened  and  weakened.     The  make 
and  break  shocks  in  the  secondary  coil  are  now 
more  uniform,  but  are  both  weaker. 

7.  Take  the  secondary  coil  out  and  place  it  across 


FIG.  21. — INDUCTION  EFFECTS  OF  CLOSING  AND  OPENING  A  SIDE  CIRCUIT  CONNECTED 
WITH  PRIMARY  COIL. 

the  direction  of  the  primary  coil  instead  of  in  its 
usual  position.  The  making  and  breaking  of  the 
primary  circuit  now  produce  no  effect  on  the 
secondary  circuit,  but  induced  currents  begin  to 
show  themselves  if  the  secondary  coil  is  placed 
obliquely  to  the  primary,  and  are  strongest  when 
the  two  coils  are  again  parallel. 

8.  Connect  up  the  battery  with  the  terminals, 
7"3,  7"4,  of  the  induction  coil  (as  in  Fig.  18),  intro- 
ducing a  simple  key  into  the  circuit.  Set  the 


PRACTICAL   PHYSIOLOGY  19 

Neef 's  hammer  in  vibration.  The  electrodes  from 
the  secondary  coil  are  to  be  applied  to  the  tongue, 
and  the  distance  of  the  secondary  from  the  primary 
coil  found  at  which  the  induced  shocks  can  just  be 
felt.  Determine  that  these  are  the  break  shocks 
by  raising  and  lowering  the  hammer  by  the  hand, 
and  thus  slowly  making  and  breaking  the  primary 
circuit  (the  key,  K*,  being  closed). 

9.  Unipolar  induction. — Detach    one    of    the 
wires  of  the  electrodes  from  the  secondary  coil  so 
that  only  one  electrode  is  connected  with  that  coil. 
Slide  the  coil  home.     Pass  a  strong  current  through 
the  primary  coil  and  set  Neef 's  hammer  going  as 
in  the  last  experiment.     It  will  be  found  that  shocks 
are  faintly  felt  by  the  tongue,  although   only  the 
one  electrode  is  in  connection  with  the  secondary  coil 
and  the  secondary  circuit  is  broken.    It  is  on  account 
of  this  possibility  of  stimulating  through  only  one 
pole  that  a  simple  key  is  never  used  in  the  second- 
ary circuit,  but  always  a  short-circuiting  key,  which 
is  introduced  in  the  manner  shown  in  Fig.  18.     No 
shocks  can  pass  to  the  electrodes  when  the  key  is 
closed,  since  the  coil  is  then  short-circuited  ;  only 
when  the  key  is  open  are  the  shocks  conducted  to 
the  electrodes.     On  the  other  hand,  in  the  primary 
or  battery  circuit  a  simple   key   must  always   be 
used  ;  were  a  short-circuiting  key  placed  here  the 
battery  would  rapidly  run  down. 

10.  Connect  up  a  battery  with  the  induction  coil, 
using  Helmholtz's  modification  (Fig.    19).     As  in 
experiment  8,  find  the  distance  of  the  secondary 
from  the  primary  coil  at  which  the  induced  shocks 


20  PRACTICAL   PHYSIOLOGY 

can  just  be  felt  on  the  tongue,  and  determine 
that  the  make  and  break  shocks  are  now  nearly 
equal  by  raising  and  lowering  the  spring  by  the 
hand.  Both  are  markedly  diminished. 


CHAPTER  II. 

Nerve-muscle  preparation. — Pith  a  frog  by 
cutting  through  the  spinal  cord  at  the  occipito- 
atlantoid  ligament  and  passing  a  blanket  pin  or 
wire  into  the  skull  and  down  the  cord.  Notice 
that  the  muscles  of  the  trunk  and  limbs  are  thrown 
into  contraction  when  the  cord  is  being  destroyed. 
Make  a  circular  incision  round  the  middle  of  the 
trunk  through  the  skin  only,  and  strip  off  the  skin 
from  both  hind  limbs.  Lay  the  frog  on  its  back  on 
the  frog-plate,  and  open  the  abdomen  and  thorax 
freely  but  carefully.  Notice  the  viscera  (Fig.  22)— 
heart  and  lungs,  liver,  stomach,  intestines,  ovaries 
and  oviducts  or  testes,  bladder.  Cut  through  the 
lower  end  of  the  rectum  and  through  its  attached 
mesentery.  On  raising  it  two  elongated  red  bodies 
— the  kidneys — are  seen  at  the  back  of  the  abdomen, 
partly  covering  the  nerves  which  are  passing  down 
to  the  hind  limbs.  Remove  the  kidneys  without 
touching  the  nerves.  Now  hold  the  frog  up  by  its 
legs  so  that  the  viscera  hang  towards  the  head,  and, 
cutting  through  the  middle  of  the  vertebral  column 
with  strong  scissors,  remove  the  fore  part  of  the 
trunk  and  the  viscera.  Lay  the  hind  part  on  the 
frog-plate,  and  note  the  several  muscles  which  are 
seen  on  the  front  and  back  of  the  lower  limbs  (Figs. 
23,  24).  The  gastrocnemius  is  generally  used  for 


22  PRACTICAL   PHYSIOLOGY 

experiments.  Tie  a  thread  round  its  tendon  (tendo 
Achillis  K  and  cut  this  away  from  the  calcaneum. 
Holding  it  by  the  thread,  tear  the  muscle  upwards 
away  from  the  tibia,  and  sever  this  bone  just  below 
the  knee. 


Fiu.  ».— V] 


«A  or  Faoc.    THZ  Lrrat  B 
PATTS  GcwexAUEix  ET  rf  AID 


I    .  .  :    T  -._   :      ------- 


Next  prepare  the  sciatic  nerve.  Separate  the 
muscles  at  the  back  of  the  thigh  by  the  aid  of  two 
pairs  of  forceps,  keeping  to  the  inner  of  the  two 
chief  intermuscular  septa,  and  the  nerve  will  be 
seen,  accompanied  by  the  femoral  vessels.  Do  not 
touch  the  nerve,  but  separate  the  muscles  from  it 
as  low  down  and  as  high  up  as  possible. 


PRACTICAL  PHYSIOLOGY 


Adductor  brevis 
Adductor  ma  gnus 


Gracilis 

Gastrocnemhs. 

TibiaHs  posticns 
Tendo  AchiTIis. 


FIG.  23.— MUSCLES  OF  FROG'S  LEG;  YEN-TEAL  ASPECT 

Next  seize  the  urostyle  with  forceps,  and  cut  it 
and  the  muscles  attached  to  it  entirely  away  with 
scissors.  The  nerves  previously  seen  behind  the 

Gl 


Rectus  anterior.  . 
Vastus  externns.  _ 


^Coccjg-eo-iliacus. 


"T  ' """  "  S      ^  JL fc'JLS 


.Ter; .  .-..:-     ift 


FIG.  24.— MUSCLES  OF  FKOG'S  LEG  ;  DOSSAL  ASPECT  (ECKE*>. 


24  PRACTICAL   PHYSIOLOGY 

kidneys  are  now  exposed  from  the  back;  they  are 
continuous  with  the  sciatic  nerve.  To  completely 
isolate  this  nerve  along  its  whole  length  sever  the 
attachment  of  the  ilium  to  the  sacrum.  Split  the 
end  of  the  spinal  column  longitudinally,  and,  hold- 
ing one-half  with  forceps,  lift  it  and  the  nerves 
issuing  from  it  up,  and  then  gradually  dissect  the 
nerves  from  above  down  by  snipping  their  lateral 
branches  wth  scissors  (without  touching  the  main 
nerve)  until  the  knee  is  nearly  reached.  Notice  that 
as  each  branch  is  snipped  the  muscles  which  it  sup- 
plies contract.  Lay  the  sciatic  nerve  thus  isolated 
upon  the  gastrocnemius  muscle.  Lastly,  cut 
through  the  middle  of  the  femur,  after  clearing  the 
muscles  away  from  its  lower  end  ;  you  now  have  a 
nerve-muscle  preparation.  Place  a  piece  of  blotting 
paper  wetted  with  normal  salt  solution1  or  Ringer's 
solution  on  the  frog-plate,  and  the  preparation 
upon  this,  laying  the  nerve  out  upon  the  wet  blot- 
ting paper.  Fix  a  pair  of  electrodes  so  that  the 
nerve  lies  across  them.  Perform  the  following 
experiments,  which  are,  for  the  most  part,  similar 
to  those  already  performed  upon  the  tongue  : 

i.  Determine  that  making  or  breaking  the  circuit 
of  a  constant  battery  is  a  stimulus  to  the  nerve, 
whereas  the  passage  of  the  current  usually2  pro- 
duces no  obvious  effect. 


1  Normal  salt  solution  is  made  by  dissolving  six  grammes  of  com- 
mon salt  in  a  litre  of  tap-water.    Ringer's  solution  is  an  improved  salt 
solution  made  by  saturating  one  litre  of  the  above  with    calcium 
phosphate  and  adding  ten  milligrammes  of  potassium  chloride. 

2  For  exceptions  see  Chapter  VII. 


PRACTICAL   PHYSIOLOGY  25 

2.  That  an  induction  shock  is  a  stimulus,  and 
that    the  break  induction  shock  is  a  far  stronger 
stimulus  than  the  make  induction  shock.     Get  the 
minimal   effect  of  each  by  sliding  the  secondary 
coil  to  the  necessary  distance  from  the  primary, 
and  make  notes  as  to  the  respective  positions  of 
the  secondary  coil. 

3.  That  it  is  possible  to  stimulate  the  nerve  when 
it  is  connected  by  only  one  wire  with  the  secondary 
coil ;  hence  the  necessity  for  using  a  short-circuit 
key  to  prevent  unipolar  induction.     It  is  best  for 


FIG.  25. — STIMULATION  OF  NERVE  BY  CONDENSER  DISCHARGE. 

this  experiment  to  place  the  secondary  coil  at  zero 
and  to  make  use  of  the  automatic  interrupter  (Fig. 
1 8).  The  nerve  should  be  raised  up  from  the  wet 
blotting  paper. 

4.  That  the  discharge  of  a  condenser  through  a 
nerve  also  acts  as  a  stimulus.  Arrange  the  appa- 
ratus as  shown  in  Fig.  25,  in  which  C  is  a  condenser 
made  by  covering  a  sheet  of  glass  with  tinfoil  on 
both  sides.  The  sheets  of  tinfoil  are  first  connected 
with  a  battery,  and  then,  by  turning  the  switch,  are 


26  PRACTICAL   PHYSIOLOGY 

connected  with  the  nerve,  the  battery  being  cut  off 
by  the  same  movement. 

5.  That  the  nerve  can  be  stimulated  by  mechan- 
ical means — e.g.,  by  tapping  it  gently  or  by  allowing 
mercury  to  drop  upon  it  from  a  height  of  three  or 
four  inches.   The  effect  of  a  mechanical  stimulus  is 
also  seen  whenever  a  nerve  is  cut  or  pinched,  but 
such  severe  injury  abolishes  its  conducting  func- 
tions. 

6.  That  the  nerve  is  stimulated  if  it  be  touched 
with  a  hot  wire. 

7.  That  it  can  be  stimulated  by  chemical  means, 
as  by  placing  wet  salt  or  strong  glycerine  upon  a 
freshly  cut  end. 

8.  That  drying  acts  as  a  stimulus  to  the  nerve. 
If  it  be  raised  off  the  wet  blotting  paper  and  begin 
to  dry,  the  muscle  will  be  observed  to  begin  to 
twitch.     The  salt  and  glycerine  in  the  last  experi- 
ment probably  also  act  by  abstracting  water. 

Preparation  of  the  sartorius  muscle. — The 
thin,  flat  sartorius  is  seen  crossing  obliquely  over 
the  front  of  the  thigh.  It  is  readily  isolated  by 
tying  a  thread  round  its  tendinous  attachment  to 
the  tibia,  cutting  this  attachment  away  from  the 
bone,  raising  the  lower  end  by  the  aid  of  the  thread, 
and  snipping  through  the  fascia  on  either  side  of  the 
muscle,  thus  separating  it  right  up  to  its  iliac  attach- 
ment. Notice  the  twitch  which  occurs  when  the, 
nerve,  which  enters  the  under  surface  about  its 
middle,  is  cut  through.  The  muscle  may  be  left 
attached  to  the  ilium,  or  its  bony  attachment  may  be 
cut  away  with  it  and  the  muscle  thus  completely 


PRACTICAL   PHYSIOLOGY 


isolated.  Its  uppermost  part  contains  no  nerve 
fibres,  and  can  be  used  to  show  that,  independently 
of  nerve,  muscle  also  responds  to  all  forms  of 
stimulation  (electrical,  mechanical,  thermal,  and 
chemical). 


CHAPTER  III. 

Kecord  of  muscular  contraction  (muscle- 
twitch). — Muscular  contractions  are  recorded 
upon  a  metal  drum  covered  with  highly  glazed 
paper,  and  caused  to  revolve  by  clockwork,  or  some 
other  form  of  motor,  at  a  regular  rate.  With  a  drum 
of  six  inches  diameter  one  revolution  in  a  second 
is  a  convenient  speed.  The  glazed  paper  is 
blackened  by  holding  a  gas  flame  against  it  while 
the  drum  is  revolving.  The  paper  must  fit  evenly 
and  tightly,  or  it  will  become  burnt. 

The  contraction  of  the  muscle  is  amplified  by  a 
lever  (myograph  lever),  which  may  be  straight,  but 
which  may  also  very  conveniently  take  the  crank 
form  (Sanderson's  myograph).  In  this  form  of 
myograph  the  lever  is  fixed  at  the  end  of  a  frog- 
cork,  to  which  the  muscle  is  fastened  by  a  pin 
passed  through  the  knee  joint ;  the  tendon  is 
attached  to  the  short  arm  of  the  lever  by  means  of 
a  thread  and  hook.  The  lever  should  be  weighted 
with  a  ten-gramme  weight,  attached  to  it  near  the 
fulcrum,  and  should  be  so  adjusted  that  when  nearly 
horizontal,  but  with  the  point  a  little  lower  than 
the  fulcrum,  the  muscle  is  stretched  by  the  weight 
and  the  connecting  thread  is  taut.  Arrange  the 
drum  in  the  primary  circuit  of  the  induction  coil 
(Fig.  26),  so  that,  as  it  revolves,  a  pin  which  pro- 


PRACTICAL   PHYSIOLOGY 


29 


jects  from  it,  by  striking  against  a  spring  fixed  out- 
side, instantaneously  makes  and  breaks  the  circuit 
at  each  revolution.  Although  two  induction  shocks 
are  thereby  produced  in  the  secondary  circuit,  they 
follow  one  another  so  closely  as  to  act  as  a  single 
stimulus.1  Either  attach  a  pair  of  electrodes  to  the 
muscle  itself  or  lay  the  nerve  upon  them.  The  elec- 


Muscle. 


Spring. 


.    Drum. 


FIG.  26.  —  GRAPHIC  RECORD  OF  MUSCLE-TWITCH.  THE  HYOGLOSSUS  (TONGUE  OF  FROG) 
is  REPRESENTED  IN  THIS  DIAGRAM  INSTEAD  OF  THE  GASTROCNEMIUS.  THE  MUSCLE 
AND  LEVER  SHOULD  BE  ON  THE  RIGHT  SIDE  OF  THE  DRUM  (WHICH  MUST  REVOLVE 
FROM  RIGHT  TO  LEFT)  ;  NOT  ON  THE  LEFT  SIDE,  AS  HERE  REPRESENTED. 

trodes  are  connected  through  a  short-circuit  key 
with  the  secondary  coil.  Before  the  lever  is  allowed 
actually  to  touch  the  cylinder  determine  that  the 
apparatus  is  all  in  working  order,  and  at  what  dis- 

JIt  is  also  possible  to  employ  a  single  induction  shock  as  the  stim- 
ulus by  introducing  a  break  key  into  the  primary  circuit  and  mak- 
ing the  pin  open  this  key  as  the  drum  revolves  ;  but  this  is  not  neces- 
sary, since  it  is  easy  with  the  arrangement  above  described  to  slide 
the  secondary  coil  at  such  a  distance  from  the  primary  that,  even  if 
the  drum  is  revolving  slowly,  only  the  break  shock  is  effective. 


-l  B.R  A»'i 


,} 


30  PRACTICAL   PHYSIOLOGY 

tance  of  the  secondary  from  the  primary  the  break 
shock  produces  its  full  effect — i.e.,  causes  a  full  con- 
traction— when  the  drum  is  made  to  revolve.  Do 
not  allow  the  muscle  to  be  fatigued  by  many  excita- 
tions before  recording  its  contraction. 

Now  bring  the  lever  point  so  as  lightly  to  touch 
the  blackened  paper,  using  the  stop  of  the  myo- 
graph  stand  to  prevent  the  possibility  of  the  point 
pressing  too  hard  against  the  paper.  When  the 
stop  is  used  in  this  way  the  lever  point  can  be 
removed  at  any  time  from  the  paper,  and  brought 
back  again  so  as  to  press  with  exactly  the  same 
force  as  before  ;  it  is  therefore  absolutely  essential 
to  make  use  of  the  stop  in  all  recording  experi- 
ments in  which  comparisons  of  different  curves 
upon  the  same  surface  have  to  be  made. 

Start  the  drum  revolving,  but  keep  the  short- 
circuit  key  closed  so  that  no  stimulus  reaches  the 
nerve  ;  the  lever  point  will  describe  a  horizontal 
line  (abscissa).  Whilst  the  drum  is  still  revolving 
open  the  short-circuit  key,  but  close  it  again  the 
instant  the  muscle  has  contracted  ;  immediately 
afterwards  remove  the  lever  point  from  the  drum 
before  this  has  had  time  to  perform  another  revolu- 
tion. A  simple  muscle  curve  will  thus  be  described. 

To  mark  the  point  of  stimulation,  move  the 
drum  slowly  round  by  hand  until  the  projecting 
pin  just  touches  the  spring  where  contact  is 
made  ;  bring  the  lever  point  against  the  smoked 
surface  as  far  as  the  stop  will  allow,  and  raise 
the  lever  about  half  an  inch  by  the  finger.  The 
distance  between  this  mark,  which  indicates  the 


PRACTICAL   PHYSIOLOGY  31 

moment  when  the  stimulus  was  put  into  the 
nerve,  and  the  rise  of  the  curve,  which  indicates 
the  commencement  of  the  contraction  of  the  mus- 
cle, gives  the  period  of  latent  stimulation.  To 
measure  this  period  as  well  as  the  duration  of  the 
contraction  and  relaxation  of  the  muscle  remove 
the  lever  point  from  the  smoked  surface,  set  the 
drum  revolving  at  the  same  rate  as  before,  and 
allow  a  tuning  fork  of  one  hundred  vibrations 
per  second  to  record  its  waves  just  below  the 
abscissa  of  the  muscle  curve,  putting  the  bristle, 
which  is  attached  to  the  tuning  fork,  for  a  second 
only  against  the  drum.  Cut  through  the  paper 
and  remove  it  carefully  from  the  drum.  Lay  it 
on  the  table,  and  write  upon  it  date  and  descrip- 
tion. Then  pass  it  through  the  varnishing  trough, 
and  hang  it  up  to  dry.  When  dry,  cut  out  the 
part  of  the  tracing  which  is  required. 

Effect  of  heat  and.  cold  on  muscle  contrac- 
tion.— The  same  nerve-muscle  preparation  may  be 
used,  the  apparatus  being  arranged  exactly  as  in 
the  last  experiment.  Mark  on  a  new  abscissa 
the  point  of  stimulation.  Then  take  the  following 
curves  on  this  abscissa  : 

1.  A  simple  muscle  curve  at  the  room  tempera- 
ture. 

2.  A  simple  curve  after  warming  the  muscle  by 
placing  over  it  for  two  or  three  minutes  a  saddle- 
shaped    brass    block  which    has    been  warmed   to 
about   30°  C.     Or  warmed  salt  solution    may  be 
dropped  upon  the  muscle. 

3.  A  simple  curve  after  cooling  the  muscle  for 


32  PRACTICAL   PHYSIOLOGY 

two  or  three  minutes  with  a  brass  block  at  the  tem- 
perature of  ice  (or  by  placing  a  piece  of  ice  in 
contact  with  the  muscle). 

Finally  take  a  tuning-fork  tracing  below  the 
abscissa. 

Notice  the  effect  of  heat  and  cold  respectively 
upon  the  period  of  latency  and  upon  the  amount 
and  duration  of  the  contraction. 

Effect  of  fatigue  on  muscular  contraction.— 
The  same  or  a  similar  nerve-muscle  preparation 
may  be  used  as  in  the  last  experiments,  but  if  the 
same  it  should  be  allowed  to  resume  the  normal 
temperature  of  the  room.  Make  a  new  abscissa, 
and  mark,  as  usual,  upon  it  the  point  of  stimula- 
tion. Take  a  normal  curve.  Remove  the  writing 
point  from  the  drum,  which  is  allowed  to  revolve 
continuously  and  to  stimulate  the  muscle  with  each 
revolution.  After  about  twenty  of  such  excita- 
tions without  record,  apply  the  lever  point  again 
to  the  drum  (making  use,  of  course,  of  the  stop), 
and  let  the  muscle  describe  another  curve  at  the 
same  place  as  the  first.  Remove  the  writing  point 
again  for  the  duration  of  about  twenty  excitations, 
and  repeat  the  above  procedure  a  number  of  times 
until  the  fatigue  curves  are  very  pronounced. 
Notice  the  effects  of  fatigue  upon  contraction, 
prolonging  the  latency  period,  diminishing  the 
amount  and  slowing  the  course  of  the  contraction, 
and  greatly  delaying,  and  at  length  even  prevent- 
ing, the  relaxation  of  the  muscle. 

A  fatigue  curve  or  series  of  curves  can  also  be 
obtained  by  recording  every  contraction — that  is,  by 


PRACTICAL   PHYSIOLOGY  33 

leaving  the  lever  point  in  contact  with  the  cylinder 
during  the  whole  course  of  the  experiment ;  but 
the  individual  curves  in  a  tracing  so  obtained  are 
very  numerous,  and  tend  somewhat  to  obscure  one 
another. 


CHAPTER  IV. 

Action  of  curari. — Destroy  the  brain  of  a  frog 
by  passing  a  sharp  splinter  of  wood  through  the 
occipital  foramen  after  cutting  through  the  occipito- 
atlantoid  ligament.  Ligature  the  blood-vessels  of 
one  leg,  taking  care  to  avoid  injuring  the  accom- 
panying sciatic  nerve.  Or  the  whole  leg  can  be 
tightly  tied  round  with  a  tape  so  as  to  stop  the 
circulation  in  it.  A  drop  of  one  per  cent,  solution 
of  curari  is  now  injected  under  the  skin  of  the  back, 
and  the  frog  is  left  for  about  an  hour.  The  drug 
will  have  penetrated  to  all  parts  except  the  liga- 
tured leg.  The  following  observations  and  experi- 
ments are  to  be  made  upon  the  curarized  animal : 

(1)  Notice  that  all  the  muscles  are    paralyzed 
except  those  of  the  ligatured  limb. 

(2)  On  tapping  any  of  the  paralyzed  parts  the 
foot  on  the  ligatured  side  is  moved. 

(3)  Strip  the  skin  off  both  legs  and  isolate  both 
sets  of  sciatic  nerves  at  the  back  of  the  abdomen. 
Tie    their   upper  ends  and   cut    them  away  from 
the  vertebral  column.     Excite  both  sets  of  nerves 
high  up,  placing  them  upon  the  same  electrodes 
and  observe  the  difference  of  effect.     Excitation 
of  the  nerve  of  the  limb  which  has  been  exposed 
to    the    poison    produces    no    contraction    of    its 
muscles  ;  excitation  of  the  nerve  of  the  ligatured 
limb   produces   the   usual    effect.      Now   stimulate 
the  muscles  of  the  two  limbs,  applying  the  elec- 


PRACTICAL   PHYSIOLOGY  35 

trodes  directly  to  them.  The  muscles  of  the 
poisoned  limb  react  like  those  of  the  normal  limb, 
but  the  liminal  stimulation1  is  greater.  Determine 
at  what  distance  of  the  secondary  coil  from  the 
primary  a  response  is  obtained  in  each  case. 

The  conclusion  is  that  neither  the  nerve  fibres, 
sensory  and  motor,  nor  the  nerve  centres,  nor  the 
muscular  fibres  are  affected,  but  that  the  poison  has 
produced  paralysis  by  severing  the  connection 
between  the  motor  nerve  fibres  and  the  muscle 
fibres,  probably  at  the  end-plates. 

Muscle  wave. — Separate  the  adductor  muscles 
(gracilis  and  semimembranosus  ;  see  Figs.  23,  24) 
of  a  frog's  leg  (which  has  been  poisoned  with  curari 
so  as  to  eliminate  the  intramuscular  nerves)  from  the 
remaining  thigh  muscles,  leaving  their  attachments 
to  the  tibia.  Cut  this  bone  through  just  below 
these  attachments,  and  also  sever  the  tibia  from 
the  femur  at  the  knee  joint.  It  is  then  easy  to 
effect  the  separation  of  the  muscles  up  to  their 
iliac  attachments ;  a  small  fragment  of  the  ilium 
may  be  cut  away  and  removed  along  with  them. 
Tie  a  thread  to  the  tibial  and  another  to  the  iliac 
attachment,  stretch  the  muscular  mass  lightly  be- 
tween these  threads,  and  fasten  the  threads  by  a 
couple  of  pins  to  the  frog-cork.  Allow  a  light 
muscle-lever  to  rest  across  the  muscles  near  one 
end.  The  movements  of  the  lever  are  recorded 
upon  a  rapidly  revolving  drum,  and  curves  are  to 
be  obtained  of  the  swelling  of  the  muscle  during 

'The  stimulation  which  is  just  effective—/.*.,  just  produces  a 
response. 


36  PRACTICAL   PHYSIOLOGY 

its  contraction  in  the  same  manner  as  the  curves  of 
shortening  of  the  gastrocnemius  were  obtained  in 
previous  experiments. 

Connect  two  pairs  of  pin  electrodes  with  a  com- 
mutator, the  cross  wires  of  which  are  removed  so 
that  it  is  used  merely  as  a  switch.  The  commutator 
is  placed  in  the  secondary  circuit.  One  pair  of  elec- 
trodes is  used  to  stimulate  the  muscles  close  to  the 
lever,  the  other  at  the  far  end  of  the  muscular  mass  ; 
the  electrodes  must  be  securely  fixed  into  the  frog- 
cork.  Describe  an  abscissa,  and  mark  the  point  of 
stimulation  as  in  previous  experiments,  making  use 
of  the  stop.  Then  take  two  tracings  of  the  contrac- 
tion of  the  muscle,  firstly  when  stimulated  close  to 
the  lever,  secondly  when  stimulated  at  the  further 
end  of  the  muscle.  In  the  latter  case  the  latency 
period  is  prolonged,  and  the  second  curve,  there- 
fore, occurs  later  than  the  other.  The  interval 
between  the  two  curves  represents*  the  time  which 
it  has  taken  for  the  wave  of  contraction  to  pass 
along  the  length  of  the  fibres  which  intervene 
between  the  two  points  which  were  successively 
stimulated.  Take  a  tuning-fork  tracing,  and  meas- 
ure this  time,  and  from  it  and  the  length  of  muscle 
traversed  by  the  wave  calculate  the  rate  of  propa- 
gation of  the  muscle  wave  per  second. 

It  is  essential  for  the  success  of  this  experiment 
that  the  muscles  used  should  have  their  fibres  run- 
ning longitudinally  and  parallel  with  one  another. 
If  the  frogs  are  large  the  two  sartorius  muscles 
may  be  used  with  advantage  instead  of  the  adduc- 
tor preparation  described. 


PRACTICAL   PHYSIOLOGY  37 

Action  of  veratrin  on  muscular  contraction. 

— The  hyoglossus  muscle — i.e.,  the  frog's  tongue- 
may  be  used.  Cut  away  the  whole  of  the  lower 
jaw,  along  with  the  tongue  and  hyoid  bone.  Tie 
a  thread  to  the  tongue  near  its  tip,  and  connect 
with  the  muscle  lever  (Fig.  26).  Fix  the  prepara- 
tion to  the  myograph  cork  by  inserting  pin  elec- 
trodes on  either  side  and  immediately  in  front  of 
the  hyoid  bone  so  that  induction  shocks  will  stimu- 
late all  the  fibres  of  the  hyoglossus  muscles. 

Take  a  muscle  curve  in  the  usual  way.  If  the 
speed  of  the  drum  is  the  same  as  before  (one 
revolution  per  second),  the  curve  is  more  pro- 
longed than  that  of  the  gastrocnemius — i.e.,  the 
contraction  is  slower.  It  is  better,  however,  for 
investigating  the  action  of  veratrin  to  use  a  less 
rapid  rate  of  cylinder,  since  this  drug  enormously 
delays  the  relaxation  of  muscle.  The  cylinder 
therefore  should  be  arranged  to  revolve  once  in 
about  four  or  five  seconds.  A  normal  muscle  curve 
is  first  described,  the  point  of  stimulation  being 
marked  in  the  usual  way.  Then  inject  with  a 
hypodermic  syringe  a  few  drops  of  veratrin  acetate 
solution  (one  per  thousand)  under  the  mucous 
membrane  of  the  tongue,  so  that  the  drug  is 
brought  into  contact  with  the  fibres  of  the  hyo- 
glossus. After  a  minute  or  two  take  another  mus- 
cle curve.  Describe  a  tuning-fork  tracing  below 
the  abscissa.  If  the  preparation  is  excited  repeat- 
edly, it  will  be  found  that  the  contractions  grad- 
ually lose  their  prolonged  character,  which,  how- 
ever, returns  after  a  period  of  rest. 


CHAPTER  V. 

Effect  of  two  successive  stimuli  upon  a  mus- 
cle-nerve preparation.  A.  Summation. — Make 
a  muscle-nerve  preparation  and  fix  it  upon  the 
myograph  in  the  usual  way,  so  that  the  muscle  writes 
its  contractions  upon  a  cylinder  revolving  about 
once  in  two  or  three  seconds.  Place  the  secondary 
coil  at  such  a  distance  from  the  primary  that  the  con- 
traction produced  is  minimal.  Now  by  means  of  a 
second  pin  projecting  from  the  drum  quite  close 
to  the  first,  allow  two  shocks  of  the  same  minimal 
intensity  to  affect  the  nerve  in  rapid  succession. 
If  the  two  pins  are  sufficiently  near  one  another 
a  simple  muscle  curve  will  again  be  described, 
but  the  contraction  will  be  more  complete  than 
with  the  single  minimal  stimulus.  If  the  stimulus 
used  is  subminimal — i.e.,  ineffective — the  effect 
of  its  repetition  may  be  to  produce  an  effective 
stimulus. 

B.  Superposition. — Place  the  secondary  coil  at 
such  a  distance  from  the  primary  that  the  excita- 
tion produced  by  a  single  projecting  pin  striking 
the  spring  in  its  revolution  is  maximal,  and  de- 
scribe a  normal  muscle  curve  in  the  usual  way. 
Then  insert  a  second  pin  at  varying  intervals  so 
that  the  excitation  which  it  produces  will  affect  the 
nerve  at  different  intervals  after  the  first  excitation; 


PRACTICAL   PHYSIOLOGY 


39 


viz.,  (a)  during  the  rise  of  the  first  curve,  (d)  near 
the  top  of  the  first  curve,  (c)  during  the  decline  of 
the  first  curve.  Take  these  double  tracings  at 
different  levels  of  the  paper,  each  one  on  its  own 
abscissa. 

Effect  of  several  successive  stimuli ;  teta- 
nus.— For  studying  the  effect  on  a  nerve-muscle 
preparation  of  a  rapid  succession  of  stimuli  a  vibrat- 
ing steel  reed  is  used  to  make  or  break  the  primary 


FIG.  27. — TETANUS  OF  MUSCLE. 


circuit  of  the  induction  coil  by  allowing  a  wire  at- 
tached to  its  end  to  dip  into  and  out  of  a  cup  of 
mercury.  The  rate  of  vibration  of  the  reed  de- 
pends upon  its  length,  which  can  be  varied  by 
clamping  it  at  different  places  ;  it  is  marked  at 
points  for  producing  vibrations  of  ten,  fifteen, 
twenty,  and  thirty  per  second  (Fig.  27).  The 
secondary  coil  should  be  placed  at  such  a  distance 
from  the  primary  that  only  the  break  shock  is 
effective.  The  drum  may  revolve  at  only  a  mod- 
erate speed  (one  revolution  in  four  or  five  seconds.) 


40  PRACTICAL   PHYSIOLOGY 

Attach  the  muscle  to  the  lever  of  the  myograph 
in  the  usual  way ;  place  the  nerve  upon  the  elec- 
trodes ;  describe  an  abscissa ;  set  the  reed  vibrat- 
ing ;  open  the  key  in  the  secondary  circuit  for 
about  a  second  ;  take  the  lever  point  away  from 
the  drum.  A  tracing  is  to  be  taken  in  this  way  at 
each  of  the  above  rates,  each  tracing  on  its  own 
abscissa ;  add  a  time  marking. 


FIG.  28. — TRANSMISSION  MYOGRAPH  OF  MAREV.  F,  FORCEPS  FOR  GRASPING  THE  MUS- 
CLE THE  CONTRACTION  OF  WHICH  is  TO  BE  RECORDED.  THE  Two  BLADES  OF  THE 
FORCEPS  ARE  DRAWN  TOGETHER  BY  AN  INDIA-RUBBER  BAND.  7",  RECEIVING  TAM- 
BOUR, THE  AlR  IN  WHICH  IS  COMPRESSED  BY  THE  SWELLING  OF  THE  MUSCLE,  AND 

FROM  WHICH  THE  PRESSURE   IS  TRANSMITTED  BY  AN  INDIA-RUBBER  TUBE  TO  T't 
THE  RECORDING  TAMBOUR,  THE  LEVER  OF  WHICH  WRITES  ON  A  REVOLVING  DRUM. 


Record  of  voluntary  contraction. — A  volun- 
tary muscular  contraction,  say  of  the  finger-muscles, 
may  be  recorded  in  the  same  way  as  the  contraction 
of  a  frog's  muscle,  by  resting  the  hand  upon  the  frog- 
plate  and  tying  a  thread  to  one  of  the  fingers,  the 
other  end  of  the  thread  being  attached  to  the  lever  ; 
this  should,  however,  either  be  furnished  with  a 
moderately  heavy  weight  or  held  down  by  a  strong 
spring  or  elastic  band.  On  abducting  the  finger 


PRACTICAL   PHYSIOLOGY  41 

the  lever  is  raised,  and  a  curve  is  described  which 
bears  a  close  resemblance  to  a  tetanus  produced 
by  ten  or  twelve  vibrations  per  second. 

Another  method  of  obtaining  such  a  curve  is  by 
the  use  of  the  transmission  myograph  (Fig.  28), 
which  consists  of  two  tambours  connected  by  india- 
rubber  tubing.  The  first  or  receiving  tambour  is 
so  arranged  against  the  muscles  of  the  ball  of  the 
thumb  that  when  these  muscles  are  made  to  con- 
tract voluntarily  the  air  within  it  is  compressed, 
and  the  differences  of  pressure  are  transmitted  to 
the  second  or  recording  tambour,  which  writes 
against  the  revolving  drum. 

Sound  of  a  voluntarily  contracting  muscle. — 
Place  the  tips  of  the  middle  fingers  in  the  ears, 
and  contract  the  muscles  of  the  arm  strongly.  A 
rumbling  sound  is  heard  which  is  generally  as- 
sumed to  be  caused  by  the  successive  contractions 
of  the  fibres,  and  to  indicate  the  rate  of  vibration 
of  the  voluntary  tetanus.  The  sound  heard  is, 
however,  probably  a  harmonic  of  the  actual  note 
produced,  the  perception  of  notes  of  so  low  a  pitch 
being  modified  by  resonance  within  the  ear. 


CHAPTER   VI. 

Work  of  muscle ;  extensibility  of  muscle. — 

The  experiments  to  be  performed  on  this  subject 
are  recorded  upon  a  stationary  drum  which  must 
be  moved  onwards  for  about  five  millimetres  by 
hand  after  each  record. 

Make  a  muscle  preparation,  preferably  the  sarto- 
rius  (p.  26),  place  it  on  the  myograph,  and  arrange 
that  it  shall  be  stimulated  by  induction  shocks.  The 
lever  should  have  a  light  scale  pan  suspended  from 
it  near  the  fulcrum  ;  such  a  scale  pan  can  readily 
be  made  from  the  lid  of  a  pill  box.  Determine  : 

1.  The   effect  upon   the   lift,  the  weight  being 
constant  (say  about  thirty  grammes),  of  a  gradual 
increase  of  the  strength  of  the  stimulus  from  mini- 
mal to  maximal. 

2.  The  amount  of  work  which  the  muscle  performs 
in  lifting  different  weights,  the  stimulus  being  con- 
stant  and   maximal.      Beginning  with   the  weight 
of  the  scale  pan  alone,  weights  are  gradually  added, 
and   the  muscle  being  stimulated,   an   ordinate  is 
described  for  each  additional  weight.     The  work 
of  the  muscle  is  estimated  as  weight   X   height. 

Another  result  is  yielded  in  this  experiment ; 
viz.,  the  effect  of  gradually  increasing  weights  in 
producing  extension  of  muscle  in  the  resting  and 
contracted  conditions  respectively.  For  it  is  ob- 
vious that  the  lowermost  point  of  any  ordinate 
described  by  a  contracting  muscle  represents  the 


PRACTICAL   PHYSIOLOGY  43 

length  to  which  the  resting  muscle  is  extended  by 
the  particular  weight,  and  the  top  of  the  ordinate 
the  length  to  which  the  muscle  when  contracted  is 
extended  by  the  same  weight.  If  the  ordinates 
are  at  regular  distances  apart  a  line  joining  their 
lowermost  ends  gives  the  curve  of  extension  of  the 
resting  muscle,  and  a  line  joining  the  tops  of  the 
ordinates  the  curve  of  extension  of  the  contract- 
ing muscle.  Further,  if  the  weights  are  removed 
in  succession  and  ordinates  are  again  described 
after  each  such  removal,  curves  of  recovery  from 
extension — i.e.,  of  retraction — can  be  obtained. 
This  experiment  can  be  conveniently  performed 
with  the  sartorius,  large  shot  serving  as  the  weights. 

3.  The  effect  of  after-loading.  Take  a  series  of 
contraction  ordinates,  using  a  maximal  stimulus 
and  a  constant  weight  (say  about  thirty  grammes). 
Begin  with  the  muscle  free  weighted,  and  by  using 
the  screw  stop  beneath  the  lever  raise  the  latter 
so  that  the  muscle  and  connecting  thread  are  some- 
what slackened.  Under  these  circumstances  the 
muscle  will  not  begin  to  raise  the  weight  until  its 
contraction  has  proceeded  to  a  certain  extent ;  this 
is  termed  after-loading.  Describe  a  series  of  con- 
traction ordinates  with  a  gradual  increase  of  after- 
load.  Estimate  the  amount  of  work  done  under 
these  conditions,  and  compare  with  that  performed 
by  the  free-weighted  muscle. 

These  experiments  on  muscle  work  and  exten- 
sion can  be  performed  either  with  single  make  or 
break  shocks,  or  by.  tetanisation  by  means  of  the 
Neef  s  hammer  of  the  induction  coil. 


CHAPTER  VII. 

Rate    of  transmission    of  nerve    impulse. — 

Make  a  nerve-muscle  preparation  in  the  usual  way ; 
fix  it  upon  the  myograph,  and  lay  the  nerve  out 
upon  two  pairs  of  electrodes,  one  placed  as  near  the 
muscle  as  possible,  the  other  close  to  the  vertebral 
column.  With  a  large  frog  nearly  two  inches  will 
intervene  between  the  two.  Place  a  commutator 
without  cross  wires  in  the  secondary  circuit,  and 
arrange  so  that  by  moving  the  bridge  of  the  com- 
mutator the  induction  shocks  can  be  switched  on 
to  one  or  other  -pair  of  electrodes.  The  drum  is 
to  be  included  in  the  primary  circuit,  and  a  short- 
circuit  key  in  the  secondary  (Fig.  29). 

Two  muscle  curves  are  now  taken  with  a  fast 
rate  of  cylinder  and  a  maximal  stimulus ;  this  is  to 
be  applied  to  the  nerve,  firstly,  close  to  the  muscle, 
and,  secondly,  close  to  the  vertebral  column.  The 
muscle  curves  are  to  be  taken  in  exactly  the  same 
way,  and  with  exactly  the  same  precautions  as  to 
the  use  of  the  stop,  etc.,  as  detailed  in  Chapter  III., 
and  the  two  curves  are  to  be  traced  upon  one  ab- 
scissa, and  a  time  tracing  written  beneath  this.  It 
will  be  found  that  the  curves  are  not  coincident, 
but  that  one  succeeds  the  other  by  a  very  small 
interval,  this  interval  representing  the  time  occu- 
pied by  the  transmission  of  the  nerve  impulse 


PRACTICAL   PHYSIOLOGY 


45 


along  the  length  of  nerve  between  the  two  pairs  of 
electrodes.  The  interval  is  relatively  small  com- 
pared with  the  total  latency  period  of  the  muscle- 
nerve  preparation  ;  it  can  be  rendered  more  evident 
if  the  nerve  (not  the  muscle)  be  cooled.  But  to 
measure  it  accurately  a  very  fast  rate  of  movement 
and  a  longer  nerve  must  be  taken.  This  is  usually 
done  by  the  use  of  the  pendulum  myograph,  upon 


FIG.  29. — EXPERIMENT  TO  DETERMINE  THE  RATE  OF  CONDUCTION  ALONG  A  MOTOR 
NERVE.  THE  MUSCLE  AND  LEVER  SHOULD  BE  ON  THE  RIGHT-HAND  SIDE  OF  THE 
DRUM  ;  NOT  ON  THE  LEFT  SIDE,  AS  REPRESENTED  IN  THE  DIAGRAM. 

which  the  contraction  of  the  thumb  muscles  in  man 
is  recorded,  the  electrodes  being  applied  over  the 
median  nerve  at  the  elbow  and  over  the  brachial 
plexus  above  the  clavicle  respectively ;  the  length  of 
nerve  thus  investigated  may  be  a  foot  or  more.  The 
muscle-contraction  is  recorded  by  means  of  tambours. 
Conduction  in  both  directions ;  Kulme's  ex- 
periment.— Remove  the  gracilis  with  part  of  its 
entering  nerve  ;  lay  it  on  a  glass  plate,  with  its  inner 
surface  uppermost.  The  nerve  is  seen  to  give 


46  PRACTICAL   PHYSIOLOGY 

branches  upwards  and  downwards  ;  as  a  matter  of 
fact  each  nerve  fibre  divides  into  two  branches,  one 
for  the  upper  and  the  other  for  the  lower  part  of 
the  muscle.  The  middle  part  of  the  muscle  can  be 
entirely  cut  away  without  injuring  these  nerves, 
and  the  two  parts  of  the  muscle  will  then  only  be 
united  by  the  forked  nerves. 

If  the  ends  of  the  nerves  in  either  of  the  pieces 
of  the  muscle  are  stimulated,  whether  electrically, 
chemically  (salt),  or  mechanically  (by  snipping  with 
scissors),  both  pieces  contract. 

A  similar  experiment  can  be  made  with  the  sar- 
torius,  the  nerve  fibres  of  which  branch  as  they  pass 
into  the  upper  end  of  the  muscle,  so  that  if  this  end 
is  split  down  the  middle,  and  the  nerve  fibres  in 
either  half  are  stimulated,  the  other  half  of  the  split 
part  contracts.  It  will  be  remembered,  however, 
that  there  are  no  nerve  fibres  at  the  very  end  of 
this  muscle,  so  that  to  get  the  desired  result — i.e., 
contraction  of  both  halves — the  muscle  must  be 
stimulated  a  short  distance  from  this  end. 

Effect  of  CO2  on  conduction  in  nerve. — Take 
a  nerve-muscle  preparation  and  lay  the  nerve  across 
and  partly  imbedded  in  a  ring  of  soft  modelling 
clay  placed  upon  a  glass  slide,  to  which  a  tube  is 
cemented  so  that  a  current  of  CO2  can  be  conducted 
over  the  nerve.  The  ring  is  covered  by  a  cover 
glass,  and  the  end  of  the  nerve  projects  beyond 
it  and  rests  upon  a  pair  of  electrodes  (Fig.  30). 

Find  the  minimal  stimulus  which  will  produce 
contraction  of  the  muscle;  then  pass  a  current  of 
CO2  over  the  intervening  nerve,  and  determine  the 


PRACTICAL   PHYSIOLOGY 


47 


effect  upon  the  conducting  power  of  .the  nerve. 
Remove  the  CO2  by  a  current  of  air,  and  repeat 
the  observation. 

Another  experiment  may  subsequently  be  made 
with  ether  vapour  instead  of  CO2. 

Electrotonic  effects  of  constant  current  on 
nerve  excitability. — Make  a  pair  of  non-polari- 
sable  electrodes  by  plugging  one  end  of  each  of  two 
short  glass  tubes  with  modelling  clay  moistened 
with  normal  saline  solution,  filling  the  tubes  with 


FIG.  30. — EFFECT  OF  CARBON  DIOXIDE  ON  CONDUCTION  IN  NERVE. 

saturated  solution  of  zinc  sulphate,  and  placing  in 
this  solution  an  amalgamated  zinc  wire  (Figs.  7,  8). 
To  these  electrodes  is  led  the  current  of  a  galvanic 
battery  consisting  of  at  least  two  cells  (Fig.  31). 
Insert  a  rheochord,  a  mercury  key,  and  a  commuta- 
tor into  this  circuit  {polarising  circuit)  ;  by  means 
of  these  the  polarising  current  can  be  varied  in 
strength  and  in  direction,  or  can  be  cut  off  or  put 
in  at  will.  Another  circuit  (exciting  circuit)  must 
also  be  put  up,  and  must  include  an  induction  coil 
with  a  mercury  key  in  the  primary  circuit ;  the 


48 


PRACTICAL   PHYSIOLOGY 


secondary  circuit  is  to  have  a  short-circuit  key,  with 
which  a  pair  of  ordinary  metallic  electrodes  are 
connected  ;  these  electrodes  are  brought  in  contact 
with  the  nerve  of  a  muscle-nerve  preparation  near 
the  muscle.  The  non-polarisable  electrodes  are 
fixed  to  the  myograph  cork,  and  the  upper  part  of 
the  nerve  is  laid  upon  them.  The  record  of  the 
muscular  contractions  obtained  is  made  on  a  sta- 
tionary drum.  Be  careful  to  keep  the  nerve  moist. 


FIG.  31. — To  TEST  THE  POLAR  EFFECTS  OF  A  CONSTANT  CURRENT  ON  NERVE 
EXCITABILITY. 


Place  the  secondary  coil  at  such  a  distance  from 
the  primary  coil  that  the  break  induction  shock 
just  produces  a  contraction.  Now  put  in  the  polar- 
ising current  first  in  an  ascending  and  secondly  in 
a  descending  direction,  and  determine  the  effect  of 
its  poles  in  diminishing  or  increasing  the  excitabil- 
ity of  the  nerve  as  tested  by  the  submaximal  stim- 
ulus employed. 

Closing  and  opening  tetanus;  Pfliiger's  law 
of  contraction. — Using  the  same  apparatus  (but 


PRACTICAL   PHYSIOLOGY 


49 


with  the  omission  of  the  induction  coil  and  its 
accessories),  test  the  so-called  law  of  contraction,  or, 
in  other  words,  the  conditions  of  excitation  of  a 
motor  nerve  by  the  making  or  breaking  of  a  con- 
stant current.  The  rheochord  is  employed  as 
before  to  vary  the  strength  of  the  current,  the  com- 
mutator to  vary  its  direction  up  or  down  the  ijerve. 
It  will  have  been  observed  in  the  last  experiment 
that  the  closing  or  opening  of  the  polarising  cur- 
rent itself  acts  as  a  stimulus  to  the  nerve,  the  result 


FIG.  32. — To  TEST  PFLUGER'S  "  LAW  OF  CONTRACTION." 

varying  with  the  direction  and  strength  of  the  cur- 
rent. The  conditions  of  this  excitation,  so  far  as 
regards  strength  and  direction  of  current,  are  now 
to  be  worked  out.  Beginning  with  a  very  weak 
current,  the  rider  of  the  rheochord  being  brought 
near  to  the  end  b  of  the  rheochord  wire  (see  Fig. 
15),  determine  the  effect  upon  the  nerve,  as  indi- 
cated by  the  contraction  of  the  muscle,  of  making 
and  breaking  the  current  when  it  is  (i)  ascending 
and  (2)  descending.  Repeat  the  experiment,  using 
a  moderate  strength  of  polarising  current — i.e.,  with 
the  rider  of  the  rheochord  near  the  end  a  of  the 


50  PRACTICAL   PHYSIOLOGY 

wire.  Finally,  the  effect  of  a  strong  current  is  to  be 
studied  by  eliminating  the  rheochord  altogether, 
and,  if  necessary,  adding  more  cells  to  the  battery. 
If  the  nerve  be  very  excitable1  the  muscle  may 
remain  in  contraction  during  the  whole  time  of  the 
passage  of  a  strong  descending  current  (closing 
tetanus),  and  may  also  remain  contracted  for  a  con- 
siderable time  after  the  removal  of  a  strong  ascend- 


Glass  rod. 


-Curarized  sartorius. 


FIG.  33. — POLAR  EFFECTS  OF  CONSTANT  CURRENT  UPON  MUSCLE. 

ing  current  (Ritters  opening  tetanus).  If  Ritter's 
tetanus  is  obtained  the  nerve  may  be  cut  between 
the  electrodes.  The  tetanus  instantly  ceases  be- 
cause the  point  where  the  stimulus  occurs  (the 
original  anode)  is  cut  off. 

That  in  closing  a  constant  current  the  excitation 

1  The  excitability  of  a  muscle-nerve  preparation  is  greatest  when 
made  from  a  frog  which  has  been  kept  in  a  cold  place  or  in  contact 
with  ice,  and  then  for  half  an  hour  at  the  ordinary  room-temperature 
pithed. 


PRACTICAL   PHYSIOLOGY  51 

occurs  at  the  kathode,  in  opening  at  the  anode,  can 
be  shown  upon  a  curarized  sartorius  laid  upon  a 
pair  of  non-polarisable  electrodes  (Fig.  33).  It 
will  be  observed  that  the  twitch  begins  at  the 
kathode  when  the  current  is  closed  ;  indeed,  the 
muscle  may  remain  more  or  less  contracted  at  that 
end  during  the  whole  time  of  the  passage  of  the 
current.  On  the  other  hand,  on  opening  the  cir- 
cuit the  twitch  begins  near  the  anode,  and  may  again 
be  followed  by  a  prolonged  contraction.  These 
prolonged  contractions  correspond  to  the  closing 


FIG.  34.— EFFECT  OF  A  CONSTANT  CURRENT  ON  NERVE  CONDUCTION. 

and  opening  tetanus  obtained  through  a  motor 
nerve.  They  show  that  excitation  is  produced  not 
only  at  the  make  and  break  but  also  during  the 
passage  and  for  a  short  time  after  the  cessation  of 
a  strong  constant  current. 

Effect  of  a  constant  current  on  conduction  in 
nerve. — Place  the  spinal  ends  of  the  two  sciatic 
nerves  of  a  frog  upon  a  single  pair  of  stimulating 
electrodes,  and  on  one  of  the  nerves  between  the 
point  to  be  stimulated  and  the  muscle  place  a  pair 
of  non-polarisable  electrodes  connected  through  a 


52  PRACTICAL   PHYSIOLOGY 

key  to  a  constant  battery  of  moderate  strength 
(Fig.  34).  Throw  in  an  ascending  current,  and  then 
faradize  both  nerves  by  the  automatic  interrupter. 
Whilst  the  muscle  in  the  one  case  will  be  tetanized 
and  speedily  fatigued,  in  the  other  case  the  ner- 
vous impulses  will  be  blocked  by  the  constant  cur- 
rent, and  there  will  be  no  contraction,  while  on 
removing  the  constant  current  the  second  muscle 
is  at  once  tetanized  by  the  faradization  of  its  nerve. 
This  experiment  was  devised  by  Bernstein  to  dem- 
onstrate the  fact  that  a  nerve  may  be  stimulated 
indefinitely  without  showing  fatigue — i.e.,  without 
its  excitability  and  conductivity  being  affected. 


CHAPTER  VIII. 

Paradoxical  contraction. — Dissect  out  the 
sciatic  nerve  of  a  frog,  cutting  all  the  branches 
save  that  to  the  calf  muscles,  but  leaving  the  cut 
branch  to  the  peronei  muscles  as  long  as  pos- 
sible. Place  the  central  cut  end  of  this  branch 
upon  the  electrodes  from  a  secondary  coil,  and 
faradize  by  rapid  induced  currents  (Fig.  35).  The 
calf  muscles  are  thrown  into  tetanus  by  reason  of 


FIG.  35. — PARADOXICAL  CONTRACTION. 

the  electrotonic  changes  which  are  produced  in  the 
sciatic  nerve  trunk. 

Secondary  contraction. — Take  a  nerve-muscle 
preparation,  and  lay  its  nerve  over  the  muscles  of 
another  leg,  the  nerve  of  which  is  placed  upon  the 
electrodes  (Fig.  36).  Tetanize  these  muscles ; 
the  nerve  of  the  first-named  preparation  will  be 
stimulated  by  the  electrical  variations  which  accom. 
pany  the  contraction  of  the  tetanized  muscles.  A 
nerve-muscle  preparation  thus  used  in  place  of  a 


54 


PRACTICAL   PHYSIOLOGY 


galvanometer    to  indicate    electrical    variations  is 
known  as  a  rheoscopic  preparation. 

Secondary  contraction  from  the  heart. — Lay 


FIG.  36. — SECONDARY  CONTRACTION. 

the  nerve  of  a  muscle-nerve  preparation  upon  the 
beating  heart.  If  the  preparation  is  very  excit- 
able the  muscle  will  be  seen  to  twitch  with  each 
beat  of  the  ventricle.  If  the  heart  beat  and  twitch 
are  both  recorded  the  twitch  will  be 
found  to  slightly  precede  the  beat — 
i.e.,  the  electrical  change'precedes  the 
mechanical  ;  this  is  seen  best  with  a 
cooled  heart. 

Contraction     without     metals ; 
Galvani's  experiment. — By  means 
of  a  glass  rod  loop  up  the  nerve  of  a 
nerve-muscle  preparation,  and  allow    FIG.  37.-coNTRAc- 
its  cut  end  to  come  in  contact  either      M^liIlTf° 
with  the  surface  of    its  own  muscle 
(Fig.  37)  or  with  other  muscles.      If  the  nerve  is 
very  excitable  there  will  be  a  contraction  of    its 
muscle   each    time   that  the  end  of    the   nerve  is 
brought  in  contact  with  the  muscle.     This  excita- 
tion is  caused  by  the  closing  through  the  nerve  of 
the  demarcation  current  of  the  muscle. 


PRACTICAL   PHYSIOLOGY  55 

Capillary  electrometer. — The  capillary  elec- 
trometer consists  essentially  of  mercury,  which  is 
forced  by  pressure  from  behind  for  a  certain  dis- 
tance into  a  glass  tube  drawn  out  to  a  capillary 
termination  ;  the  free  end  of  the  capillary  is  filled 
with  dilute  sulphuric  acid  and  dips  into  a  vessel 
containing  the  same  fluid.  The  capillary  is  ob- 
served with  a  microscope.  If  the  mercury  and  the 
sulphuric  acid  be  now  connected  with  wires  which 
are  charged  with  electricity  there  is  produced  a 
movement  of  the  mercury  in  the  direction  which  the 
current  would  take — i.e.,  from  positive  to  negative 
— the  extent  of  movement  of  the  meniscus  being, 
roughly  speaking,  proportioned  to  the  difference 
of  potential.  From  the  direction  and  extent  of 
the  movement  the  direction  and  electromotive 
force  of  the  current  can  therefore  be  gauged. 

Join  a  pair  of  non-polarisable  electrodes  up  in 
circuit  with  a  capillary  electrometer  and  Daniell 
cell  through  a  rheochord  and  commutator  in  the 
manner  shown  in  the  diagram  (Fig.  38),  but  with 
a  piece  of  blotting  paper  moistened  with  salt 
solution  placed  across  the  electrodes  instead  of 
the  muscle  shown  in  the  figure.  Put  a  short- 
circuiting  key  between  the  electrometer  and  the 
electrodes.  Have  the  short-circuiting  key  shut 
at  first  so  that  the  electrometer  is  short-circuited, 
and  the  battery  key  open.  Bring  the  mercury 
meniscus  into  the  field  of  the  microscope.  Now 
open  the  short-circuiting  key.  If  the  electrodes 
are  themselves  without  current  there  will  be  no 
effect  on  the  electrometer ;  but  usually  there  is  a 


PRACTICAL   PHYSIOLOGY 


slight  effect,  the  direction  and  the  amount  of  which 
should  be  noticed.  Next  close  the  battery  circuit, 
leaving  the  short-circuiting  key  open.  Part  of  the 
battery  current  is  now  sent  through  the  electrodes 
and  electrometer  in  a  particular  direction  (which 
can  be  reversed  by  the  commutator),  and  there  is 
a  corresponding  movement  of  the  mercury.  Note 


Sulphuric  acid __ 

Meniscus  of 
mercury 


Tube  for  trans- 
mitting pres- 
sure to  mercury 


Mercury   passing 
into  capillary 


Dilute  sulphuric 
acid  . 


Mercury  . 


.  .Non-polarisable 
electrodes. 


FIG.  38.— ARRANGEMENT  FOR  EXAMINING  MUSCLE  CURRENT  BY  CAPILLARY  ELECTRO- 
METER. A,  DIAGRAM  OF  ELECTROMETER;  B,  THE  CAPILLARY  AS  SEEN  WITH  THE 
MICROSCOPE. 

the  direction  of  this  movement,  and  by  following 
out  the  wires  from  the  battery  determine  with  which 
part  of  the  electrometer  the  anode  and  kathode 
are  respectively  connected.  By  means  of  the 
rheochord  and  commutator  a  definite  proportion 
of  the  battery  current  can  be  sent  in  either  direc- 
tion through  the  electrodes — i.e.,  through  any 
preparation  with  which  they  may  be  connected. 


PRACTICAL   PHYSIOLOGY  57 

Open  the  battery  key  and  close  the  short-circuiting 
key  ;  the  meniscus  should  return  to  its  original  posi- 
tion. Lay  a  muscle,  which  may  have  one  end  cut  or 
injured,  upon  the  electrodes  in  place  of  the  wet  blot- 
ting paper.  Place  it  with  one  electrode  touching 
the  longitudinal  surface  and  the  other  at  or  near 
the  injured  end.  Then  open  the  short-circuiting 
key  to  allow  the  demarcation  current  of  the  muscle 
to  affect  the  electrometer.  From  the  direction  of 
movement  of  the  mercury  determine  the  direction 
of  the  muscle  current  through  the  apparatus.  The 
electromotive  force  of  the  current  can  be  measured 
by  closing  the  battery  key,  so  that  the  battery 
current  is  brought  into  the  circuit,  and  by  aid  of 
the  rheocord  and  commutator  sending  a  current 
through  the  circuit  in  a  direction  the  reverse  of  the 
demarcation  current  and  of  exactly  such  a  strength 
(as  measured  by  the  position  of  the  rider  on  the 
rheocord)  as  to  bring  the  mercury  back  to  zero. 

G-alvaiiometer. — Substitute  in  the  above  experi- 
ment a  high-resistance  galvanometer  (Fig.  39)  for 
the  electrometer,  and  repeat  the  above  observa- 
tions, using  the  movement  of  the  needle  as  the 
index  instead  of  the  mercury  of  the  electrometer. 

Having  with  either  the  electrometer  or  galvano- 
meter determined  the  existence  and  direction  of  a 
current  in  muscle,  tetanize  a  muscle  through  its  nerve 
as  it  lies  upon  the  non-polarisable  electrodes,  and  no- 
tice the  diminution  of  the  excursion  of  the  mercury 
or  of  the  magnetic  needle  which  occurs  on  stimula- 
tion (negative  variation  of  the  demarcation  current). 

.The  demarcation  and  excitation  currents  of  nerve 


58  PRACTICAL   PHYSIOLOGY 

are  examined  and  measured  in  exactly  the  same 
way  as  those  of  muscle. 

Excitation  current  of  heart  muscle. — Con- 
nect the  non-polarisable  electrodes  of  the  electro- 
meter with  a  beating  frog-heart,  which  may  either 
be  removed  from  the  body  and  laid  with  the 


Galvanometer. .  - 


FIG.  39. — ARRANGEMENT  FOR  EXAMINING  MUSCLE  CURRENT  BY  GALVANOMETER. 

base  of  the  ventricle  upon  one  electrode  and  the 
apex  on  the  other,  or  left  in  situ  and  the  elec- 
trodes connected  with  apex  and  base  of  ventricle 
by  thick  threads  wetted  with  salt  solution.  Each 
contraction  of  the  ventricle  is  accompanied  by  a  to 
and  fro  movement  of  the  mercury  meniscus  of  the 
electrometer,  the  direction  of  which  may  be  noted 
and  the  alterations  in  electrical  potential  of  base 
and  apex  deduced  therefrom.1 

1  An  accurate  record  of  changes  in  electrical  potential  can  be  ob- 
tained by  photographing  the  excursions  of  the  mercury  meniscus. 


CHAPTER  IX. 

Involuntary  muscle. — Cut  a  transverse  strip 
from  the  stomach  of  a  recently  fed  frog,  and  attach 
to  a  light  muscle  lever  in  exactly  the  same  way  as 
with  a  voluntary  muscle.  Keep  moist  with  Ringer's 
solution.  Allow  the  lever  to  write  upon  a  very 
slowly  revolving  drum.  Place  a  pair  of  stimulating 
electrodes  in  contact  with  the  fixed  end  of  the  strip, 
and  excite  by  allowing  the  drum  to  make  and  break 
a  galvanic  circuit.  Record  the  resulting  contraction 
and  determine  its  period  of  latency. 

The  strip  will  probably  be  found  to  contract 
spontaneously  and  rhythmically  after  a  time.  Re- 
cord these  contractions. 

The  frog-heart.— Examine  the  contracting 
heart  of  a  pithed  frog,  cutting  away  the  sternum 
and  ensiform  cartilage  and  the  front  of  the  peri- 
cardium. Gently  raise  the  tip  of  the  ventricle  with 
a  blunt  hook,  and  tie  a  thread  to  the  pericardial  liga- 
ment which  binds  the  ventricle  to  the  back  of  the 
pericardium.  Cut  the  ligament  beyond  the  thread 
and  raise  the  heart  by  the  latter.  Do  not  grasp 
the  heart  with  forceps. 

Notice  the  sinus  venosus  receiving  the  two  venae 
cavae  superiores  and  the  vena  cava  inferior;  the 
double  auricle  ;  the  single  ventricle  ;  and  on  the 
front  the  bulbus  aortse  leaving  the  ventricle  and 


6o 


PRACTICAL   PHYSIOLOGY 


dividing  into  two  branches,  each  of  which  again 
soon  divides  into  three  (Figs.  40,  41,  and  43). 


Right  auricle . 
Bulbusaortae 


Left  auricle. 


Ventricle. 


FIG.  40. — FROG'S  HEART  ;  VENTRAL  ASPECT  (£CKER). 

Effect  of  heat  and  cold  on  rate  of  beat. — 

Count  the  number  of  beats  per  minute.  Now  apply, 
first,  a  cooled  and,  second,  a  warmed  wire  (a)  to 
the  ventricle,  (<$)  to  the  auricles,  (r),  by  turning  up 
the  heart,  to  the  sinus.  Count  the  rate  immedi- 


Left  superior  vena  cava  ... 


Left  auricle.. 
Opening  from  sinus  into 

right  auricle..  _- 


Sinus  venosus  cut  open..---" 


Pulmonary  vein. 
..Right  superior  vena  cava. 

.  .Right  auricle. 


Ventricle. 
Inferior  vena  cava. 


FIG.  41. — FROG'S  HEART;  DORSAL  ASPECT  (ECKER). 

ately  after  each  application.     If  desired  the  effects 
may  be  recorded  in  the  manner  described  below. 
Stannius'    experiment. — Raise     the    ventricle 


PRACTICAL   PHYSIOLOGY 


6l 


carefully,  and,  passing  a  thread  under  the  sinus, 
tighten  it  round  the  sino-auricular  junction,  which 
is  marked  by  a  whitish  line  (x  in  Fig.  43).  The 
sinus  continues  to  beat  as  before,  but  the  auricle 
and  ventricle  come  to  a  standstill  in  diastole,  con- 
tracting, however,  each  time  they  are  stimulated, 
whether  electrically  or  mechanically  (prick).  Now 
tie  a  second  ligature  round  the  auriculo-ventricu- 
lar  junction.  The  ventricle  usually  gives  a  few 
beats,  and  then  again  comes  to  a  permanent  stand- 


Olfactory  lobes. 

Cerebral  hemispheres. 
Thalamus  with  pineal  gland. 
Optic  lobes. 
-VTI  lU_  Cerebellum. 

Medulla  oblongata. 
Spinal  cord. 


FIG.  42. — BRAIN  OF  FROG  in  Situ,  EXPOSED  BY  REMOVING  THE  ROOF  OF  THE  CRANIUM. 

still.  It  can,  however,  be  made  to  beat  by  artificial 
stimulation  (prick,  electric  shock),  and  the  curve 
which  is  obtained,  if  it  be  recorded  in  the  same  way 
as  the  record  of  an  ordinary  muscle  twitch  (i.e.,  by 
attaching  the  ventricle-apex  by  means  of  a  hook 
and  thread  to  a  lever,  as  in  Fig.  44),  is  similar  to 
the  latter  except  that  all  parts  of  the  curve,  includ- 
ing the  period  of  latent  stimulation,  are  much  pro- 
longed. 

The  following  points  can  be  made  out  in  the  Stan- 
nius'  preparation,  viz.:  (i)  Any  excitation  of  cardiac 
muscle  which  is  adequate  to  produce  a  contraction 


62 


PRACTICAL   PHYSIOLOGY 


produces  a  full  contraction  (all  or  none),  (2)  dur- 
ing both  the  period  of  latency  and  the  progress  of 
the  contraction  produced  by  one  excitation  the 
muscle  gives  no  response  to  a  second  excitation; 
in  other  words,  there  is  a  prolonged  refractory 
period,  (3)  no  superposition  is  produced  by  succes- 
sive stimuli,  and  therefore  no  true  tetanus,  (4)  after 


PRACTICAL   PHYSIOLOGY 


a  period  of  rest  there  is  a  slight  increase  in  the  ex- 
tent of  the  first  few  succeeding  contractions,  the 
second  curve  being  a  little  higher  than  the  first, 
the  third  than  the  second,  and  so  on  (staircase  phe- 
nomenon of  Bow  ditch). 

Cardiac  nerves. — Destroy  by  a  wire  the  spinal 
cord  of  a  frog,  and  also  remove  the  cerebral  hemi- 
spheres ;  this  can  be  done  without  special  dissec- 


AA. 


FIG.  44. — FROG  CARDIOGRAPH.    r 


tion  by  cutting  away  the  upper  jaw  and  anterior 
part  of  the  skull  at  the  level  of  the  front  of  the 
tympana  (see  Fig.  42).  The  posterior  part  of  the 
brain  with  the  medulla  oblongata  must  not  be 
injured.  Fix  a  pair  of  pin  electrodes  passed 
through  a  small  cork  into  this  part  of  the  brain 
and  arrange  for  tetanization.  ,  Lay  the  frog  upon 
its  back  on  the  frog-cork  ;  expose  the  heart  and 
the  chief  nerves  which  are  proceeding  from  the 
base  of  the  skull  to  the  hyoid  region  (vagus,  glosso- 
pharyngeal,  and  hypoglossal ;  see  Fig.  43).  The  var 


64  PRACTICAL   PHYSIOLOGY 

gus  gives  off  a  small  branch  on  each  side,  which  runs 
close  along  the  superior  vena  cava  to  the  sinus  ve- 
nosus.  Place  the  vagus  trunk  upon  a  fine  pair  of 
wire  electrodes  passed  through  a  flat  piece  of  cork 
(which  must  itself  be  fixed  securely  by  pins  to  the 
frog-cork),  and  connect  these  electrodes,  and  also 
those  which  are  fixed  into  the  brain,  to  a  commu- 
tator without  cross  wires  so  that  the  faradizing 
shocks  can  be  sent  to  one  or  other  pair  as  may  be 
desired.  Place  the  frog-cork  upon  the  stand  of  a 
frog  cardiograph  (Fig.  44),  and  by  means  of  a 
thread  and  fine  steel  hook  attach  the  apex  of  the 
ventricle  to  the  light  lever  of  the  apparatus,  and 
record  the  contractions  of  the  heart  upon  a  very 
slowly  moving  drum  (one  revolution  in  four  or  five 
minutes).  Be  careful  not  to  injure  the  heart  more 
than  is  absolutely  necessary.  It  is  well,  in  order 
to  fix  the  preparation  securely,  to  pass  a  pin  close 
to  the  base  of  the  heart  through  the  vertebral 
column  into  the  frog-cork.  The  following  experi- 
ments may  be  performed  upon  this  preparation  : 

1.  Take  a  normal  tracing  of  the  beats  during 
about  a  minute. 

2.  Whilst  this  is  proceeding  stimulate  not  too 
strongly  the  medulla  oblongata,  allowing  the  result 
to  be  recorded. 

3.  Cut  the  vagi  nerves  near  the  skull  and  repeat 
the  above  experiment.   No  effect  should  be  obtained. 

4.  After  the  normal  contractions  are  resumed 
stimulate  the  vagus,  and  again  record  the  result. 
With  weak    stimulation   of    this   nerve   the   heart 
may  beat  faster  and  more  strongly  owing  to  exci- 


PRACTICAL   PHYSIOLOGY  65 

tation  of  the  sympathetic  fibres  which  have  joined 
the  vagus  near  the  skull  and  are  running  with  the 
cardiac  branches  to  the  heart ;  with  stronger  stimu- 
lation the  heart  will  beat  more  slowly  and  less 
vigorously  or  may  stop  altogether. 

5.  Place  a  drop  or  two  of  a  weak  solution  (0.2 
per  cent.)   of  nicotin  upon  the  heart,  and  after  a 
minute    or    two    again    stimulate    the    vagus ;    no 
effect  should  be  obtained,  since  nicotin  blocks  the 
junction  of  the  nerve  fibres  with  the  distributing 
nerve    cells    within    the    heart.     Wash    away    the 
nicotin  with  salt  solution,  and   the  effect  will  re- 
turn after  a  time. 

6.  Disconnect     the    electrodes     which    are    at- 
tached to  the  skull  from  the  commutator,  and  use 
them  to  stimulate  the  heart  itself  at  the  white  line 
of  the    sino-auricular   junction.     (The    electrodes 
must  not  be  held  in  the  hand,  but  must  be  fixed 
in  position  by  a  pin  through  their  cork  or  other- 
wise.)    The  heart  again  comes  to  a  standstill   in 
diastole.      Record  this  effect  also. 

Notice  that  in  each  case  there  is  an  after-effect 
of  a  nature  contrary  to   the  immediate   effect. 

7.  Drop  a  very  small  quantity  of  dilute  solution 
of  muscarin   upon  the  sinus,  recording  the  effect 
produced  upon  the  rate   and    force   of    the    beat. 
After  a  short  time  the  heart  will  probably  come 
to  a  standstill  in  diastole.      Now  wash  away  the 
muscarin  with  two  or  three  drops  of  solution  of 
atropin  sulphate  (i   in  300).      Notice  the  gradual 
restoration  of    the  rate   and  force    of    the    beats. 
Notice    further    that    no    inhibition    can    now  be 

5 


66  PRACTICAL  PHYSIOLOGY 

produced  on  stimulating  either  the  vagus  or  the 
sino-auricular  junction.  There  may,  however,  be 
acceleration  from  stimulation  of  the  sympathetic 
fibres,  which  are  running  to  the  heart  in  the 
vagus. 


CHAPTER  X. 


Perfusion  of  frog-heart. — Expose  the  heart  of 
a  large  pithed  frog  ;  remove  the  pericardium  and 
cut  through  the  pericardial  ligament.  Raise  the 
apex  of  the  ventricle  with  a  blunt  hook  ;  make  a 
free  cut  with  scissors  into  the  auricles  thus  ex- 
posed, near  to  the  sino-auricular  junction  ;  insert 
the  scissors  into  the  auricles  and  snip  through 
their  septum.  Wash  all  blood  away  with  salt 
solution.  Place  a  loop  of  cotton  around  the  auri- 
cles near  to  their  junction  with  the  ventricles  ;  in- 
sert the  double  perfusion  cannula  of  the  heart 
plethysmograph  (Fig.  45)  through  the  auricles 


4  _-  Perfusion  cannula 
("natural  size). 


Beaker  for  overflow 

Perfusion  cannula 

Heart  tied  on  perfusion 

cannula 


FIG.  45.— FROG-HEART  PLETHYSMOGRAPH. 


68  PRACTICAL   PHYSIOLOGY 

and  into  the  ventricle,  and  tie  it  in  firmly  by  means 
of  the  ligature  round  the  auricles  ;  cut  through 
the  sinus,  and  remove  the  heart  upon  the  cannula. 
Now  place  the  heart  in  the  plethysmograph,  which 
must  be  full  of  oil,  both  stop-cocks  being  closed  ; 
then  open  the  one  belonging  to  the  bent  tube.  The 
inlet  tube  of  the  perfusion  cannula  is  connected  to  a 
reservoir  containing  Ringer's  solution,  and  the  out- 
let tube  conducts  to  a  receptacle  into  which  the  fluid 
may  flow  after  passing  through  the  heart.  If  the 
reservoir  of  Ringer's  fluid  be  at  a  height  of  three 
or  four  inches  above  the  heart  the  ventricle  will 
presently  begin  to  beat,  and  its  changes  in  volume 
will  cause  a  movement  of  the  oil  to  and  fro  in  the 
open  tube.  If  this  be  now  closed  and  the  one  con- 
taining the  piston  opened  the  piston  will  move  to 
and  fro,  and  its  movements  can  be  recorded  on  a  very 
slowly  rotating  horizontal  drum.  (See  diagram.) 

The  influence  of  various  salts,  such  as  chloride 
of  calcium  and  chloride  of  potassium,  and  of  drugs, 
such  as  veratrin,  can  be  studied  by  adding  definite 
amounts  of  them  to  the  Ringer's  solution  used  for 
perfusion. 

Perfusion  through  vessels. — Tie  a  small  simple 
glass  cannula  into  the  aorta  of  a  large  pithed  frog  ; 
it  can  either  be  passed  directly  into  the  cut  aorta 
or  more  easily  through  a  cut  in  the  ventricle.  The 
cannula  must  be  filled  with  Ringer's  solution,  and 
connected  through  an  india-rubber  tube  with  a 
reservoir  of  the  same  fluid.  Suspend  the  frog  by 
a  pin  through  the  jaw,  and  fix  the  reservoir  a  short 
distance  above  the  head  so  that  the  fluid  flows 


PRACTICAL   PHYSIOLOGY  69 

into  the  vessels  by  gravitation.  Make  a  cut  into 
the  sinus  venosus  so  that  the  Ringer's  fluid  may 
flow  freely  out  after  it  has  traversed  the  blood-ves- 
sels of  the  body  ;  the  escaping  fluid  will  drop  from 
the  toes.  Count  the  number  of  drops  per  minute, 
and  repeat  the  counting  two  or  three  times  ;  it  will 
be  found  that  the  flow  is  fairly  regular. 

To  test  the  effect  of  drugs  upon  the  muscular 
tissue  of  the  arterioles  the  drug  to  be  tested  is 
added  in  known  quantity  to  the  circulating  fluid, 
and  by  again  counting  the  number  of  drops  per 
minute  it  can  be  determined  whether  the  arterioles 
are  becoming  dilated  or  contracted  as  the  effect  of 
the  drug.  This  experiment  may  be  tried  with  a 
decoction  of  suprarenal  capsule. 


CHAPTER  XI. 

Study  of  the  chief  vascular  and  respiratory 
mechanisms:  1.  Action  of  the  heart  in  man. — 

Observe  the  chest  wall  over  the  situation  of  the 
heart ;  notice  and  feel  the  impulse  or  apex  beat, 
strongest  at  one  spot.  Apply  the  ear  directly  or 
through  a  stethoscope  over  this  spot,  and  make  out 
the  two  cardiac  sounds.1  Whilst  listening  to  the 
sounds  of  the  heart  feel  the  pulse  of  the  subject,  and 
determine  that  the  first  sound  is  systolic — t.e.t  is 
synchronous  with  the  rise  of  pressure  in  the  artery 
due  to  the  contraction  of  the  ventricle.  Next 
apply  the  button  of  a  cardiograph  to  the  point 
where  the  impulse  is  most  distinct,  and  take  a 
tracing  upon  a  moderately  fast  drum  by  the  aid  of 
a  recording  tambour.  The  breath  may  be  held 
whilst  the  tracing  is  taken,  so  as  to  eliminate  the 
movements  caused  by  respiration. 

2.  Methods  of  determining  the  pressure  and 
velocity  of  the  blood  in  the  arteries. — The  chief 
methods  used  can  be  studied  upon  a  system  of  india- 
rubber  tubes  through  which  water  is  pumped  by  a 
Higginson  syringe.  With  this  system  mercurial  and 
other  manometers  and  the  stromuhr  and  other  in- 

1  The  second  is  heard  most  distinctly  over  the  second  right 
costo-sternal  articulation. 


PRACTICAL   PHYSIOLOGY  71 

struments  for  measuring  or  estimating  velocity  can 
be  successively  connected  by  means  of  T-tubes. 

3.  The  pulse  in  the  arteries. — Feel  the  pulse  in 
the  radial  artery  and  determine  (i)  its  rate,  (2)  its 
quality,    whether  hard  or  soft,   bounding,    readily 
compressible,   etc.  ;    then    apply  a  sphygmograph, 
either  Marey's  original  pattern  or  the  modification 
devised  by  Dudgeon.      Use  such  a  pressure  upon 
the  spring  of  the  sphygmograph  as  will  allow  the 
variations  in  pressure  within  the  artery  to  be  most 
manifest.     The  tracings  are  taken  on  slips  of  paper 
smoked  over  a  candle.    Write  on  each  slip  the  name 
of  the  subject  of  the  experiment  and  the  pressure 
which  was  employed  ;  varnish  and  preserve. 

4.  Arterial  pressure  in  man. — The  pressure  of 
the  blood  within  the  human  arteries  can  be  deter- 
mined by   applying  over  any  artery,  such  as  the 
radial,  the  sphygmoscope  of  Hill  or  the  sphygmo- 
dynamometer  of  Oliver.      Both  these  instruments 
are  adapted  for  showing  the  variations  in  pressure 
which  accompany  the  pulse,  and  it  is  found  that 
these  fluctuations  are  best  indicated  when  the  pres- 
sure of  the  instrument  upon  the  artery  is  the  same 
as  the  average  pressure  of  the  blood  within  the 
vessel.     The  point,   therefore,  around  which    the 
largest  fluctuations  oscillate  indicates  the  average 
blood  pressure. 

5.  The  respiratory  movements  in  man. — Ex- 
amine the  chest  during  quiet  respiration,  and  notice 
the  parts  in  which  most  movement  is  evident ;  the 
same  with  forced  respiration.     Observe  the  altera- 
tion in  obliquity  "and  other  changes  in  position  of 


72  PRACTICAL   PHYSIOLOGY 

the  ribs,  rib  cartilages,  sternum,  and  epigastrium. 
Apply  the  ear  directly  or  through  a  stethoscope  to 
the  :hest  wall,  and  listen  to  the  vesicular  murmur. 
Lastly  apply  a  stethograph  (Marey's  or  Sander- 
son's) to  the  chest,  and  register  the  movements  of 
respiration  by  means  of  a  recording  tambour  upon 
a  slowly  moving  drum. 


CHAPTER  XII. 

Reflex  action. — A  decerebrate  frog  is  sus- 
pended by  the  lower  jaw.  The  following  experi- 
ments are  to  be  made  upon  it : 

1.  Gently  pinch  the  toe  of  one  foot  with  forceps  ; 
the  leg  is  drawn  up.     When  again  quiescent  pinch 
the  toe  more  firmly  ;   not  only  the  one,  but  both 
legs  are  drawn  up,  and  there  may  also  be  a  move- 
ment of  the  upper  limbs  (spread  of  excitation). 

2.  Stimulate  the  toe  (a)  with  single  and  (<5)  with 
interrupted  induced  currents.      Determine  at  what 
distance  of  the  secondary  coil  from  the  primary 
the  reflex  response  is  elicited  in  each  case  (effect 
of  summation). 

3.  Touch  one  flank  with  a  glass  rod  moistened 
with  acetic  acid  ;  the  foot  of  the  same  side  is  raised 
to  rub  off  the  irritant ;  if  that  foot  is  held  down  the 
other  foot  may  be  used  {purposeful  actio^i) . 

4.  Having  washed  off  the  acetic  acid  and  allowed 
the  frog  to  become  quiescent  allow  the  extremity 
of  the  toes  to  dip  into  dilute  sulphuric  acid  (i  per 
1,000).       Count    the    time  in   half-seconds    which 
elapses  between  the  application  of  the  acid  and  the 
withdrawal  of  the  toe.     Wash  the  acid  off  immedi- 
ately after  the  withdrawal.    Repeat  this  observation 
at  intervals  of  a  few  minutes,  and  take  the  average 
time  of  response  (Turc&s  method). 


74  PRACTICAL   PHYSIOLOGY 

Next  place  a  crystal  of  chloride  of  sodium  upon 
the  optic  lobes,  and  again  determine  the  time  of 
response  after  application  of  the  dilute  sulphuric 
acid  to  the  toes.  It  will  probably  be  found  to  be 
decidedly  longer  (inhibition  of  reflex  by  descending 
excitation  ;  Setschenows  experiment}. 

5.  Lay  the  frog  upon  the  frog-cork ;    open  the 
abdomen  and  draw  out  a  loop   of   intestine  ;  the 
heart  is  also  to  be  sufficiently  exposed  for  its  beats 
to  be  observed.     Now  excite  the  intestine  strongly, 
either  by  induction  shocks  or  mechanically  by  a 
pinch  or  blow.     The  effect  will  be  to  produce  a 
slowing  or  complete  stoppage  of  the  heart,  which 
will,  however,  soon  recommence  beating  (reflex  in- 
hibition of  heart). 

6.  Inject  a  very  small  dose  of  strychnin  (i  drop 
of  a  i   per  1,000  solution)  under   the    skin    of  a 
decerebrate  frog,  and  wait  for  a  few  minutes  until 
it  is  absorbed  into  and  distributed  by  the  circula- 
tion.    It  will  then  be  found  that  the  slightest  touch 
of  the  skin  produces  not  a  simple  purposeful  reflex 
action,  but  convulsive  contractions  of  all  the  mus- 
cles in  the  body. 

Reaction  time  in  man. — The  reaction  time  in 
man  may  be  determined  by  an  arrangement  of 
electric  signals,  but  is  done  more  simply  by  Wal- 
ler's apparatus.  This  consists  of  two  wooden  lev- 
ers lying  across  a  piece  of  india-rubber  tube, 
one  end  of  which  is  closed,  the  other  being  con- 
nected with  a  tambour  which  writes  upon  a  drum, 
the  speed  of  which  should  be  moderate.  A  screen 
is  used  to  hide  the  movements  of  the  experimenter 


PRACTICAL   PHYSIOLOGY  75 

from  the  person  experimented  on.  The  latter  sits 
at  the  table  with  one  finger  resting  lightly  on  one  of 
the  levers.  He  is  to  respond  by  pressing  the  lever 
the  instant  he  (a)  feels  a  tap  on  that  finger,  his  eyes 
being  shut ;  (fr)  hears  a  tap  on  the  second  lever  ;  (c) 
sees  the  movement  which  is  imparted  to  the  second 
lever  by  the  experimenter,  who  presses  it  down  on 
the  other  side  of  the  screen.  In  each  case  two 
marks  are  recorded  upon  the  abscissa,  one  being 
that  which  is  made  by  the  experimenter  in  impart- 
ing the  stimulus  and  the  other  that  made  by  the 
observed  person  in  responding.  The  interval  be- 
tween the  two  marks,  which  can  be  accurately 
measured  by  the  aid  of  a  tuning-fork  tracing,  indi- 
cates the  time  between  stimulus  and  response — • 
i.e.,  the  reaction  time — in  the  case  of  each  of  the 
three  senses.  To  record  this  with  any  accuracy  a 
large  number  of  observations  must  be  made  with 
each  method  of  stimulation  and  the  average  time 
taken. 

Discrimination  time. — For  the  measurement  of 
this  the  observed  person  places  one  finger  upon 
the  end  of  each  lever.  It  is  agreed  beforehand 
that  he  is  only  to  react  to  a  stimulus  received  on 
the  one  side,  not  on  the  other.  The  experimenter 
may  stimulate  either.  It  will  be  found  that  the 
reaction  time  is  lengthened  by  a  certain  interval, 
and  this  increase  of  reaction  time  is  termed  the 
discrimination  time. 

Volitional  time. — Similar  observations  are 
made,  but  with  the  understanding  that  it  is  only 
the  hand  on  the  side  which  receives  the  stimulus 


76  PRACTICAL   PHYSIOLOGY 

which  is  to  be  used  for  the  response.  The  reac- 
tion time  is  now  found  to  be  still  more  lengthened 
because  the  observed  person  has  to  make  a  double 
decision  ;  viz.,  to  determine  not  only  which  of  the 
two  hands  has  been  stimulated,  but  also  which  one 
he  has  to  use  in  response  to  the  signal. 


A  List  of  Works  in  Medicine  and  Surgery 

PUBLISHED   BY 

LONGMANS,  GREEN,  &  CO. 


ASHBY,  WRIGHT  and  NORTHRUP. 
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ASHBY.  Works  by  HENRY  ASHBY,  M.D. 
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School  of  Medicine. 

Health  in  the  Nursery.  With  25  Illus- 
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Notes  on  Physiology.  Seventh  Edition, 
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On  the  Use  of  Massage  and  Early  Pas- 
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The  Present  Position  of  the  Treat- 
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BRODIE.  The  Essentials  of  Experi- 
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Demonstrator  of  Pathology  in  the  Royal 
College  of  Surgeons,  Ireland  ;  late  Medical 
Travelling  Prizeman  of  Dublin  University, 
etc.,  etc.  With  221  Illustrations,  partly 
in  colors,  a  Chromo-lithographic  Plate,  7 
Photographic  Plates,  and  full  Index.  Royal 
8vo.  Pp.  xvi-456.  $7-5°* 

WILKS  AND  MOXON.  Lectures  on 
Pathological  Anatomy.  By  SAMUEL 
WILKS,  M.D.,  F.R.S.,  Consulting  Physi- 
cian to  Guy's  Hospital,  and  the  late  WAL- 
TER MOXON,  M.D.,  F.R.C.P.,  some  time 
Lecturer  on  Pathology  at  Guy's  Hospital. 
8vo.  $6- oof 


A  List  of  Works  in  Medicine  and  Surgery. 


MEDICAL   AND    SURGICAL   WORKS.— Continued. 


WEYSSE.  An  Epitome  of  Human 
Histology  for  the  use  of  Students  in 
connection  with  Lectures  and  Labora- 
tory Work.  By  ARTHUR  W.  WEYSSE, 
A.M.,  Ph.D.  Instructor  in  Biology,  Mas- 
sachusetts Institute  of  Technology,  Boston, 
8vo.  $1.50* 

WILLIAMS.  Diseases  of  the  Upper 
Respiratory  Tract:  the  Nose,  Pharynx 
and  Larynx.  With  a  Section  on  the 
Examination  of  the  Ear.  By  P.  WAT- 
SON WILLIAMS,  M.D.,  London,  Physician 
in  Charge  of  the  Throat  Department  at  the 
Bristol  Royal  Infirmary,  etc.,  etc.  With  37 
Colored  and  Stereoscopic  Plates  and  a 
Stereoscope.  8vo,  page  xxiv-413.  $6.00* 


WILLIAMS.  Pulmonary  Consump- 
tion :  its  Etiology,  Pathology,  and  Treat- 
ment. By  C.  J.  B.  WILLIAMS,  M.D., 
LL.D.,  F.R.S.,  Physician-Extraordinary 
to  Her  Majesty  the  Queen,  and  CHARLES 
THEODORE  WILLIAMS,  Physician  to  the 
Hospital  for  Consumption  and  Diseases  of 
the  Chest,  Brompton.  Second  Edition, 
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Plates  and  10  Wood-cuts.  8vo.  466  pages. 

$5- oof 


VETERINARY  SCIENCE,   ETC. 


FITZWYGRAM.  Horses  and  Stables. 
By  Lieut. -General  SIR  F.  FITZWYGRAM, 
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$1.50 

MILES.  The  Horse's  Foot  and  How 
to  Keep  it  Sound.  By  WILLIAM  MILES. 
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Royal  8vo.  $4.  sof 

MORTON.  A  Manual  of  Pharmacy  for 
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By  W.  J.  T.  MORTON.  Eighth  Edition. 
I2mo.  5 76  pages.  $3-5of 

PERCIVALL.  Works  by  WILLIAM  PER- 
CIVALL,  M.R.C.S. 

Hippopathology.  A  Systematic  Treatise 
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tions. 8vo.  $3.00 


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Published  by  Longmans,  Green,  &  Co. 


SANITARY  ENGINEERING 

A    Practical    Treatise    on   the  Collection,   Removal   and   Final 

Disposal  of  Sewage  and  the  Design  and  Construction 

of  Works  of  Drainage  and  Sewerage 

With  a  Special  Chapter  on  the  Disposal  of  House  Refuse  and  Sewage  Sludge,  and 
Numerous  Hydraulic  Tables,  Formulae  and  Memoranda,  including  an  Exten- 
sive Series  of  Tables  of  Velocity  and  Discharge  of  Pipes  and  Sewers, 
specially  computed   by  Ganguillet  and    Kutter's   Formula 

By  Colonel   E.  C.  S.  MOORE,  R.E. 

Author  of  "  Sanitary  Engineering  Notes,"  etc.    Formerly  Instructor  in  Estimating 
and  Construction  at  the  School  of  Military  Engineering,  Chatham. 

Large  8vo,  with  534  Illustrations  and  70  Large  Folding  Plates.     Pp.  xxvii-62i,  $10.00  net. 

Summary  of  Contents  :  Introduction.  Chapter  I. — Collection  and  Removal.  II.  Sewer- 
age. III.  The  Flow  of  Liquid  in  Pipes  and  Open  Channels.  IV.  Hydraulic  Memoranda — 
Hydraulic  Tables.  V.  Application  of  Formulae  of  Durcy  and  Bazin,  and  also  of  Ganguillet 
and  Kutter.  VI.  Construction  and  Materials.  VII.  Ventilation.  VIII.  Traps.  IX.  Appa- 
ratus, Latrines  and  W.  C.'s.  X.  Apparatus  (continued),  Urinals,  Lavatory  Fittings,  etc. 
XI.  Surface  Water  Collection.  XII.  Subsoil  Drainage.  XIII.  Sanitary  Notes.  XIV. 
Sewage  Disposal.  XV.  Disposal  of  Sludge  and  House  Refuse. 

The  following  are  some  of  the  leading  features  of  this  important  work  : 

a.  The  entirely  new  and  extended  series  of  tables  of  velocity  and  discharge  of  circular  and 

egg-shape  sewers,  etc.     This  is  the  first  published  series  of  such  tables,  based  upon 
Kutter's  formula  and  they  have  been  specially  calculated  for  the  work. 

b.  The  full  manner  in  which  all  sections  of  the  subject  are  illustrated,  both  by  lithographic 

plates  and  smaller  illustrations  in  the  text. 

c..  The  special  descriptions,  with  illustrations  of  important  works  of  Sewerage  and  Sewage 
Disposal  and  the  valuable  information  on  the  Disposal  and  Destruction  of  House 
Refuse  and  Sludge. 

d.  The  important  information  on  the  flow  of  water  in  Pipes  and  Open  Channels. 

e.  The  extensive  series  of  Hydraulic  and  other  Tables  beyond  those  just  mentioned. 

Considering  the  grave  importance  of  Sanitary  Engineering,  it  is  remarkable  that  no  book 
dealing  with  the  subject  in  a  thorough  and  comprehensive  manner  has  hitherto  been  published. 

In  the  preparation  of  the  work  Colonel  Moore  has  availed  himself  of  valuable  information 
furnished  by  leading  specialists  in  particular  branches  of  the  subject,  one  of  whom  is  the  late 
Colonel  Waring,  whose  work  in  the  disposal  of  sewage  and  garbage  is  described  at  length. 

OPINIONS   OF    THE  PRESS. 

"  No  engineer  can  afford  to  be  without  a  copy  of  this  comprehensive  manual  of  sanitary  engineering.     .     .     . 

"  The  book  is  ...  full  and  complete  epitome  of  the  latest  practice  in  sanitary  engineering  ;  a  glance  at  the 
list  of  authorities  quoted  at  the  commencement  of  the  work  will  show  how  thorough  and  how  painstaking  Colonel 
Moore  has  been.  .  .  .  As  a  book  of  reference  it  is  simply  indispensable." — The  Public  Health  Engineer. 

"  Few  departments  of  applied  science  can  show  greater  or  more  dangerous  errors  than  are  revealed  in  the 
history  of  sanitation,  but  a  volume  like  this  shows  the  immense  progress  which  has  been  made,  and  leads  us  to 
think  that  at  last  we  are  on  firm  ground  ...  a  great  book,  involving  almost  infinite  labor  on  the  part  of  the 
author,  and  can  be  recommended  as  undoubtedly  the  standard  work  on  the  subject.  .  .  .  The  type  is  ex- 
cellent, the  misprints  remarkably  few,  the  illustrations  in  the  text  most  clearly  drawn  and  reproduced,  and  the 
folding  plates  are  models  of  what  such  plates  ought  to  be." — The  Builder. 

"  It  is  the  only  book  yet  received  by  The  Engineering  Record  which  presents  a  good  description  of  the 
various  biological  systems  of  sewage  disposal  now  attracting  so  much  attention.  It  contains  a  large  number  of  new 
hydraulic  tables  of  undoubted  value  as  time  and  labor-saving  aids  in  computations.  Its  illustrations  of  sewer  de- 
tails are  numerous  and  well  chosen.  The  subject  of  disposal  in  general  is  treated  in  an  interesting  manner,  and 
the  information  on  British  systems  of  refuse  cremation  it  will  be  difficult  to  secure  elsewhere  in  so  convenient  a 
form.  .  .  .  The  book  is  very  good  from  beginning  to  end,  and  will  be  a  valuable  addition  to  the  library  of  any 
one  who  wishes  to  learn  the  general  theory  and  practice  of  so  much  of  sanitary  engineering  practice  in  Great 
Britain  as  is  embraced  in  its  scope.  The  discussion  of  various  theories  of  the  flow  in  sewers,  and  the  tables  to 
assist  in  applying  them,  is  a  feature  which  is  alone  worth  the  price  of  the  volume." 

—Engineering  Record,  New  York. 


Longmans,  Green,  &  Co.,  91  and  93  Fifth  Ave.,  New  York. 


A  List  of  Works  in  Medicine  and  Surgery. 


A  Dictionary  of  Applied  Chemistry 


BY 


T.  E.  THORPE,  B.Sc.  (ViCT.),  PH.D.,  D.Sc.  (DUEL.),  F.R.S, 

PROFESSOR   OF   CHEMISTRY    IN   THE   ROYAL   COLLEGE   OF   SCIENCE,    LONDON. 

ASSISTED  BY  EMINENT  CONTRIBUTORS. 


PUBLISHED    IN    THREE    VOLUMES. 

VOL.  I.  (A— DY.)     With  236  Illustrations.     Pp.  724,  8vo, $15. oo 

VOL.  II.  (E — NU.)     With  240  Illustrations.     Pp.  722,  8vo, 15.00 

VOL.  III.  (O— Z.)     With  352  Illustrations.     Pp.  1,066,  8vo, 20.00 


ADVERTISEMENT. 

This  Work  is  essentially  a  Dictionary  of  Chemistry  in  its  Applications  to  the  Arts  and  Manufactures  ;  hence 
it  deals  but  sparingly  with  the  purely  scientific  aspects  of  Chemistry,  unless  these  have  some  direct  and  immediate 
bearing  upon  the  business  of  the  technologist.  For  all  such  matters  reference  is  made  to  the  New  Edition  of 
"  Watt's  Dictionary  of  Chemistry,"  by  Dr.  Forster  Morley  and  Mr.  Pattison  Muir,  to  which,  indeed,  the  present 
Work  may  be  said  to  be  complementary.  In  order  to  facilitate  such  reference  the  general  plan  and  method  ol 
arrangement  of  the  two  Dictionaries  are  similar,  and  the  nomenclature  and  notation  adopted  are  practically 
identical.  It  has,  however,  not  been  thought  desirable,  even  if  it  had  been  found  possible,  to  make  use  of  the  same 
elaborate  system  of  abbreviation  and  contracted  expression  as  that  employed  in  the  companion  Work,  in  which  the 
variety  and  complexity  of  the  subject-matter  are  necessarily  much  greater. 

Although  the  two  Works  are,  in  a  broad  general  sense,  complementary,  it  is  practically  impossible  to  avoid  a 
certain  amount  of  overlapping,  and  therefore  a  certain  degree  of  independence.  Hence  in  the  present  Work  the 
Chemical  history  of  a  product  of  technical  importance,  so  far  as  it  is  known,  has  often  been  completed,  although  its 
derivatives  have,  at  present,  no  applications  in  the  Arts.  Moreover,  such  subjects  as  the  ATMOSPHERE,  WATER, 
FERMENTATION,  the  CHEMISTRY  OF  THE  HYDROCARBONS,  the  VEGETO-  ALKALOIDS,  GLUCOSIDES,  etc.,  etc.,  all  of 
which  are  dealt  with  in  the  other  Work,  find  also  a  place  in  this  Dictionary  by  reason  of  their  relations  to  Tech- 
nology or  to  Medicine  and  Sanitation.  In  all  cases,  however,  these  subjects  are  treated  from  the  stand-point  of 
practical  application. 

The  Editor  has  been  fortunate  in  securing  the  co-operation  of  a  large  number  of  gentlemen,  not  only  in  the 
United  Kingdom,  but  also  in  America,  Germany,  Switzerland,  Russia,  and  France,  as  contributors  on  subjects 
with  which  they  are  specially  qualified  to  deal.  A  list  of  these,  with  the  titles  of  their  contributions,  is  prefixed  to 
each  volume.  Their  names  and  standing  are  a  sufficient  guarantee  that  no  pains  have  been  spared  to  make  the 
Work  a  faithful  record  of  the  present  condition  of  Chemistry  in  its  relations  to  the  Arts  and  Manufactures.  Special 
attention  has  been  paid  to  the  bibliography  of  the  subjects,  and  in  certain  cases  to  the  compilation  of  trustworthy 
patent-lists. 


SOME   OPINIONS  OF   THE  PRESS. 


"  Should  be  in  the  hands  of  every  manufacturer  who 
wishes  to  be  well  posted  in  the  subjects  with  which  he 
has  to  do." — Iron  and  Steel  Trades  Journal. 

"  The  list  of  the  names  of  contributors  and  the  selec- 
tion of  their  subjects  inspires  confidence  at  once." — 
Journal  of  Society  of  Chemical  Industry. 

"Will  be  universally  appreciated  by  technical  and 
manufacturing  chemists.  .  .  .  Dr.  Thorpe's  great 
work  carries  with  it  its  own  emphatic  recommendation. 
It  must  prove  most  valuable,  not  merely  to  chemists  and 
chemical  manufacturers,  but  to  all  merchants  who  have 
to  deal  with  chemical  products." — Chemical  Nevus. 


'  '  The  completion  of  this  important  work  places  at  the 
service  of  manufacturers  and  others  a  complete  encyclo- 
paedia treating  of  industrial  operations  which  in  any- 
way involve  a  knowledge  of  chemistry,  and  it  cannot 
fail  to  prove  a  valuable  source  of  information  for  all  who 
are  interested  in  the  productive  arts.  .  .  .  We  feel 
confident  that  those  who  may  desire  to  keep  abreast  of 
the  progress  made  in  chemical  industries,  and  to  pos- 
sess a  trustworthy  source  of  information  concerning 
modern  chemical  arts  and  operations,  cannot  do  bet- 
ter than  provide  themselves  with  a  copy  of  Professor 
Thorpe's  admirable  '  - 

try.' "  — 


Dictionary  of  Applied  Chemis- 
— Pharmaceutical  Journal. 


A  Prospectus  of  the  work  with  Specimen  Pages  may  be  had,  post  free,  of  the  Publishers. 


Longmans,  Green,  &  Co.,  91  and  93  Fifth  Ave.,  New  York. 


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